This update for squid fixes the following issues: squid was updated to version 4.13 :

CVE-2020-24606: Fix livelocking in peerDigestHandleReply (bsc#1175671).

CVE-2020-15811: Improve Transfer-Encoding handling (bsc#1175665).

CVE-2020-15810: Enforce token characters for field-name (bsc#1175664).

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

According to the versions of the squid package installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - An issue was discovered in Squid before 4.12 and 5.x     before 5.0.3. Due to use of a potentially dangerous     function, Squid and the default certificate validation     helper are vulnerable to a Denial of Service when     opening a TLS connection to an attacker-controlled     server for HTTPS. This occurs because unrecognized     error values are mapped to NULL, but later code expects     that each error value is mapped to a valid error     string.(CVE-2020-14058)

  - An issue was discovered in     http/ContentLengthInterpreter.cc in Squid before 4.12     and 5.x before 5.0.3. A Request Smuggling and Poisoning     attack can succeed against the HTTP cache. The client     sends an HTTP request with a Content-Length header     containing '+\ '-' or an uncommon shell whitespace     character prefix to the length     field-value.(CVE-2020-15049)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The version of Tencent Linux installed on the remote TencentOS Server 3 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2022:0124 advisory.

    Package updates are available for TencentOS Server 3 that fix the following vulnerabilities:

    CVE-2019-12519:
    An issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid     calls ESIExpression::Evaluate. This function uses a fixed stack buffer to hold the expression while it's     being evaluated. When processing the expression, it could either evaluate the top of the stack, or add a     new member to the stack. When adding a new member, there is no check to ensure that the stack won't     overflow.

    CVE-2019-12520:
    An issue was discovered in Squid through 4.7 and 5. When receiving a request, Squid checks its cache to     see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request.
    If found, it servers the request. The absolute URL can include the decoded UserInfo (username and     password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to     provide a username that has special characters to delimit the domain, and treat the rest of the URL as a     path or query string. An attacker could first make a request to their domain using an encoded username,     then when a request for the target domain comes in that decodes to the exact URL, it will serve the     attacker's HTML instead of the real HTML. On Squid servers that also act as reverse proxies, this allows     an attacker to gain access to features that only reverse proxies can use, such as ESI.

    CVE-2019-12521:
    An issue was discovered in Squid through 4.7. When Squid is parsing ESI, it keeps the ESI elements in     ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is     parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this     buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same     structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.

    CVE-2019-12523:
    An issue was discovered in Squid before 4.9. When handling a URN request, a corresponding HTTP request is     made. This HTTP request doesn't go through the access checks that incoming HTTP requests go through. This     causes all access checks to be bypassed and allows access to restricted HTTP servers, e.g., an attacker     can connect to HTTP servers that only listen on localhost.

    CVE-2019-12524:
    An issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to     see if the request should be denied. Squid by default comes with rules to block access to the Cache     Manager, which serves detailed server information meant for the maintainer. This rule is implemented via     url_regex. The handler for url_regex rules URL decodes an incoming request. This allows an attacker to     encode their URL to bypass the url_regex check, and gain access to the blocked resource.

    CVE-2019-12525:
    An issue was discovered in Squid 3.3.9 through 3.5.28 and 4.x through 4.7. When Squid is configured to use     Digest authentication, it parses the header Proxy-Authorization. It searches for certain tokens such as     domain, uri, and qop. Squid checks if this token's value starts with a quote and ends with one. If so, it     performs a memcpy of its length minus 2. Squid never checks whether the value is just a single quote     (which would satisfy its requirements), leading to a memcpy of its length minus 1.

    CVE-2019-12526:
    An issue was discovered in Squid before 4.9. URN response handling in Squid suffers from a heap-based     buffer overflow. When receiving data from a remote server in response to an URN request, Squid fails to     ensure that the response can fit within the buffer. This leads to attacker controlled data overflowing in     the heap.

    CVE-2019-12527:
    An issue was discovered in Squid 4.0.23 through 4.7. When checking Basic Authentication with     HttpHeader::getAuth, Squid uses a global buffer to store the decoded data. Squid does not check that the     decoded length isn't greater than the buffer, leading to a heap-based buffer overflow with user controlled     data.

    CVE-2019-12528:
    An issue was discovered in Squid before 4.10. It allows a crafted FTP server to trigger disclosure of     sensitive information from heap memory, such as information associated with other users' sessions or non-     Squid processes.

    CVE-2019-12529:
    An issue was discovered in Squid 2.x through 2.7.STABLE9, 3.x through 3.5.28, and 4.x through 4.7. When     Squid is configured to use Basic Authentication, the Proxy-Authorization header is parsed via uudecode.
    uudecode determines how many bytes will be decoded by iterating over the input and checking its table. The     length is then used to start decoding the string. There are no checks to ensure that the length it     calculates isn't greater than the input buffer. This leads to adjacent memory being decoded as well. An     attacker would not be able to retrieve the decoded data unless the Squid maintainer had configured the     display of usernames on error pages.

    CVE-2019-12854:
    Due to incorrect string termination, Squid cachemgr.cgi 4.0 through 4.7 may access unallocated memory. On     systems with memory access protections, this can cause the CGI process to terminate unexpectedly,     resulting in a denial of service for all clients using it.

    CVE-2019-13345:
    The cachemgr.cgi web module of Squid through 4.7 has XSS via the user_name or auth parameter.

    CVE-2019-18676:
    An issue was discovered in Squid 3.x and 4.x through 4.8. Due to incorrect input validation, there is a     heap-based buffer overflow that can result in Denial of Service to all clients using the proxy. Severity     is high due to this vulnerability occurring before normal security checks; any remote client that can     reach the proxy port can trivially perform the attack via a crafted URI scheme.

    CVE-2019-18677:
    An issue was discovered in Squid 3.x and 4.x through 4.8 when the append_domain setting is used (because     the appended characters do not properly interact with hostname length restrictions). Due to incorrect     message processing, it can inappropriately redirect traffic to origins it should not be delivered to.

    CVE-2019-18678:
    An issue was discovered in Squid 3.x and 4.x through 4.8. It allows attackers to smuggle HTTP requests     through frontend software to a Squid instance that splits the HTTP Request pipeline differently. The     resulting Response messages corrupt caches (between a client and Squid) with attacker-controlled content     at arbitrary URLs. Effects are isolated to software between the attacker client and Squid. There are no     effects on Squid itself, nor on any upstream servers. The issue is related to a request header containing     whitespace between a header name and a colon.

    CVE-2019-18679:
    An issue was discovered in Squid 2.x, 3.x, and 4.x through 4.8. Due to incorrect data management, it is     vulnerable to information disclosure when processing HTTP Digest Authentication. Nonce tokens contain the     raw byte value of a pointer that sits within heap memory allocation. This information reduces ASLR     protections and may aid attackers isolating memory areas to target for remote code execution attacks.

    CVE-2019-18860:
    Squid before 4.9, when certain web browsers are used, mishandles HTML in the host (aka hostname) parameter     to cachemgr.cgi.

    CVE-2020-11945:
    An issue was discovered in Squid before 5.0.2. A remote attacker can replay a sniffed Digest     Authentication nonce to gain access to resources that are otherwise forbidden. This occurs because the     attacker can overflow the nonce reference counter (a short integer). Remote code execution may occur if     the pooled token credentials are freed (instead of replayed as valid credentials).

    CVE-2020-14058:
    An issue was discovered in Squid before 4.12 and 5.x before 5.0.3. Due to use of a potentially dangerous     function, Squid and the default certificate validation helper are vulnerable to a Denial of Service when     opening a TLS connection to an attacker-controlled server for HTTPS. This occurs because unrecognized     error values are mapped to NULL, but later code expects that each error value is mapped to a valid error     string.

    CVE-2020-15049:
    An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A     Request Smuggling and Poisoning attack can succeed against the HTTP cache. The client sends an HTTP     request with a Content-Length header containing +\ - or an uncommon shell whitespace character prefix     to the length field-value.

    CVE-2020-15810:
    An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP     Request Smuggling attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This     allows any client, including browser scripts, to bypass local security and poison the proxy cache and any     downstream caches with content from an arbitrary source. When configured for relaxed header parsing (the     default), Squid relays headers containing whitespace characters to upstream servers. When this occurs as a     prefix to a Content-Length header, the frame length specified will be ignored by Squid (allowing for a     conflicting length to be used from another Content-Length header) but relayed upstream.

    CVE-2020-15811:
    An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP     Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This     allows any client, including browser scripts, to bypass local security and poison the browser cache and     any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing     the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request     inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request     delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any     downstream caches.

    CVE-2020-24606:
    Squid before 4.13 and 5.x before 5.0.4 allows a trusted peer to perform Denial of Service by consuming all     available CPU cycles during handling of a crafted Cache Digest response message. This only occurs when     cache_peer is used with the cache digests feature. The problem exists because peerDigestHandleReply()     livelocking in peer_digest.cc mishandles EOF.

    CVE-2020-8449:
    An issue was discovered in Squid before 4.10. Due to incorrect input validation, it can interpret crafted     HTTP requests in unexpected ways to access server resources prohibited by earlier security filters.

    CVE-2020-8450:
    An issue was discovered in Squid before 4.10. Due to incorrect buffer management, a remote client can     cause a buffer overflow in a Squid instance acting as a reverse proxy.

Tenable has extracted the preceding description block directly from the Tencent Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Rocky Linux 8.6 host has packages installed that are affected by multiple vulnerabilities as referenced in the CIQ ciqsa-2026_0262 advisory.

    This advisory aggregates security fixes for the squid SRPM in CIQ LTS 8.6. It addresses 50 CVEs:
    CVE-2019-12520, CVE-2019-12524, CVE-2013-1839, CVE-2021-28116, CVE-2019-12529, and 45 more.

Tenable has extracted the preceding description block directly from the CIQ security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Rocky Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RLSA-2020:4743 advisory.

  - An issue was discovered in Squid through 4.7 and 5. When receiving a request, Squid checks its cache to     see if it can serve up a response. It does this by making a MD5 hash of the absolute URL of the request.
    If found, it servers the request. The absolute URL can include the decoded UserInfo (username and     password) for certain protocols. This decoded info is prepended to the domain. This allows an attacker to     provide a username that has special characters to delimit the domain, and treat the rest of the URL as a     path or query string. An attacker could first make a request to their domain using an encoded username,     then when a request for the target domain comes in that decodes to the exact URL, it will serve the     attacker's HTML instead of the real HTML. On Squid servers that also act as reverse proxies, this allows     an attacker to gain access to features that only reverse proxies can use, such as ESI. (CVE-2019-12520)

  - An issue was discovered in Squid through 4.7. When Squid is parsing ESI, it keeps the ESI elements in     ESIContext. ESIContext contains a buffer for holding a stack of ESIElements. When a new ESIElement is     parsed, it is added via addStackElement. addStackElement has a check for the number of elements in this     buffer, but it's off by 1, leading to a Heap Overflow of 1 element. The overflow is within the same     structure so it can't affect adjacent memory blocks, and thus just leads to a crash while processing.
    (CVE-2019-12521)

  - An issue was discovered in Squid before 4.9. When handling a URN request, a corresponding HTTP request is     made. This HTTP request doesn't go through the access checks that incoming HTTP requests go through. This     causes all access checks to be bypassed and allows access to restricted HTTP servers, e.g., an attacker     can connect to HTTP servers that only listen on localhost. (CVE-2019-12523)

  - An issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to     see if the request should be denied. Squid by default comes with rules to block access to the Cache     Manager, which serves detailed server information meant for the maintainer. This rule is implemented via     url_regex. The handler for url_regex rules URL decodes an incoming request. This allows an attacker to     encode their URL to bypass the url_regex check, and gain access to the blocked resource. (CVE-2019-12524)

  - An issue was discovered in Squid before 4.9. URN response handling in Squid suffers from a heap-based     buffer overflow. When receiving data from a remote server in response to an URN request, Squid fails to     ensure that the response can fit within the buffer. This leads to attacker controlled data overflowing in     the heap. (CVE-2019-12526)

  - An issue was discovered in Squid before 4.10. It allows a crafted FTP server to trigger disclosure of     sensitive information from heap memory, such as information associated with other users' sessions or non-     Squid processes. (CVE-2019-12528)

  - An issue was discovered in Squid 2.x through 2.7.STABLE9, 3.x through 3.5.28, and 4.x through 4.7. When     Squid is configured to use Basic Authentication, the Proxy-Authorization header is parsed via uudecode.
    uudecode determines how many bytes will be decoded by iterating over the input and checking its table. The     length is then used to start decoding the string. There are no checks to ensure that the length it     calculates isn't greater than the input buffer. This leads to adjacent memory being decoded as well. An     attacker would not be able to retrieve the decoded data unless the Squid maintainer had configured the     display of usernames on error pages. (CVE-2019-12529)

  - Due to incorrect string termination, Squid cachemgr.cgi 4.0 through 4.7 may access unallocated memory. On     systems with memory access protections, this can cause the CGI process to terminate unexpectedly,     resulting in a denial of service for all clients using it. (CVE-2019-12854)

  - An issue was discovered in Squid 3.x and 4.x through 4.8. Due to incorrect input validation, there is a     heap-based buffer overflow that can result in Denial of Service to all clients using the proxy. Severity     is high due to this vulnerability occurring before normal security checks; any remote client that can     reach the proxy port can trivially perform the attack via a crafted URI scheme. (CVE-2019-18676)

  - An issue was discovered in Squid 3.x and 4.x through 4.8 when the append_domain setting is used (because     the appended characters do not properly interact with hostname length restrictions). Due to incorrect     message processing, it can inappropriately redirect traffic to origins it should not be delivered to.
    (CVE-2019-18677)

  - An issue was discovered in Squid 3.x and 4.x through 4.8. It allows attackers to smuggle HTTP requests     through frontend software to a Squid instance that splits the HTTP Request pipeline differently. The     resulting Response messages corrupt caches (between a client and Squid) with attacker-controlled content     at arbitrary URLs. Effects are isolated to software between the attacker client and Squid. There are no     effects on Squid itself, nor on any upstream servers. The issue is related to a request header containing     whitespace between a header name and a colon. (CVE-2019-18678)

  - An issue was discovered in Squid 2.x, 3.x, and 4.x through 4.8. Due to incorrect data management, it is     vulnerable to information disclosure when processing HTTP Digest Authentication. Nonce tokens contain the     raw byte value of a pointer that sits within heap memory allocation. This information reduces ASLR     protections and may aid attackers isolating memory areas to target for remote code execution attacks.
    (CVE-2019-18679)

  - Squid before 4.9, when certain web browsers are used, mishandles HTML in the host (aka hostname) parameter     to cachemgr.cgi. (CVE-2019-18860)

  - An issue was discovered in Squid before 4.12 and 5.x before 5.0.3. Due to use of a potentially dangerous     function, Squid and the default certificate validation helper are vulnerable to a Denial of Service when     opening a TLS connection to an attacker-controlled server for HTTPS. This occurs because unrecognized     error values are mapped to NULL, but later code expects that each error value is mapped to a valid error     string. (CVE-2020-14058)

  - An issue was discovered in http/ContentLengthInterpreter.cc in Squid before 4.12 and 5.x before 5.0.3. A     Request Smuggling and Poisoning attack can succeed against the HTTP cache. The client sends an HTTP     request with a Content-Length header containing +\ - or an uncommon shell whitespace character prefix     to the length field-value. (CVE-2020-15049)

  - Squid before 4.13 and 5.x before 5.0.4 allows a trusted peer to perform Denial of Service by consuming all     available CPU cycles during handling of a crafted Cache Digest response message. This only occurs when     cache_peer is used with the cache digests feature. The problem exists because peerDigestHandleReply()     livelocking in peer_digest.cc mishandles EOF. (CVE-2020-24606)

  - An issue was discovered in Squid before 4.10. Due to incorrect input validation, it can interpret crafted     HTTP requests in unexpected ways to access server resources prohibited by earlier security filters.
    (CVE-2020-8449)

  - An issue was discovered in Squid before 4.10. Due to incorrect buffer management, a remote client can     cause a buffer overflow in a Squid instance acting as a reverse proxy. (CVE-2020-8450)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

According to its banner, the version of Squid running on the remote host is 2.x prior to 4.12 or 5.x prior to 5.0.3. It is,therefore, affected by multiple vulnerabilities:
  - Multiple denial of service (DoS) vulnerabilities exist in the SMP cache and TLS handshake implementations of Squid.   An unauthenticated, remote attacker can exploit these issues, by sending specially crafted requests to an affected   instance, to impose a DoS condition on the application (CVE-2020-14058, CVE-2020-14059). 

  - A cache poisoning vulnerability exists in Squid due to insufficient user input validation. An authenticated, remote   attacker can exploit this issue, to affect the integrity of the contents returned to users from the cache   (CVE-2020-15049).

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

According to the versions of the squid package installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - Squid before 4.9, when certain web browsers are used,     mishandles HTML in the host (aka hostname) parameter to     cachemgr.cgi.(CVE-2019-18860)

  - An issue was discovered in Squid before 4.13 and 5.x     before 5.0.4. Due to incorrect data validation, HTTP     Request Smuggling attacks may succeed against HTTP and     HTTPS traffic. This leads to cache poisoning. This     allows any client, including browser scripts, to bypass     local security and poison the proxy cache and any     downstream caches with content from an arbitrary     source. When configured for relaxed header parsing (the     default), Squid relays headers containing whitespace     characters to upstream servers. When this occurs as a     prefix to a Content-Length header, the frame length     specified will be ignored by Squid (allowing for a     conflicting length to be used from another     Content-Length header) but relayed     upstream.(CVE-2020-15810)

  - An issue was discovered in     http/ContentLengthInterpreter.cc in Squid before 4.12     and 5.x before 5.0.3. A Request Smuggling and Poisoning     attack can succeed against the HTTP cache. The client     sends an HTTP request with a Content-Length header     containing '+\ '-' or an uncommon shell whitespace     character prefix to the length     field-value.(CVE-2020-15049)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4895-1 advisory.

    Alex Rousskov and Amit Klein discovered that Squid incorrectly handled certain Content-Length headers. A     remote attacker could possibly use this issue to perform an HTTP request smuggling attack, resulting in     cache poisoning. This issue only affected Ubuntu 20.04 LTS. (CVE-2020-15049)

    Jianjun Chen discovered that Squid incorrectly validated certain input. A remote attacker could use this     issue to perform HTTP Request Smuggling and possibly access services forbidden by the security controls.
    (CVE-2020-25097)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
140446	SUSE SLES12 Security Update : squid (SUSE-SU-2020:2443-1)	Nessus	SuSE Local Security Checks	9/9/2020	6/3/2021	high
142069	EulerOS 2.0 SP5 : squid (EulerOS-SA-2020-2273)	Nessus	Huawei Local Security Checks	10/30/2020	2/13/2024	high
238736	TencentOS Server 3: squid:4 (TSSA-2022:0124)	Nessus	Tencent Local Security Checks	6/16/2025	12/5/2025	critical
356925	Rocky Linux 8.6 [CIQ] Security Update: squid / squid-debuginfo / squid-debugsource Multiple Vulnerabilities (ciqsa-2026_0262)	Nessus	Rocky Linux Local Security Checks	10/1/2026	10/11/2026	critical
184691	Rocky Linux 8 : squid:4 (RLSA-2020:4743)	Nessus	Rocky Linux Local Security Checks	11/6/2023	11/6/2023	critical
139912	Squid 2.x < 4.12 / 5.x < 5.0.3 (SQUID-2020:5, SQUID-2020:6 & SQUID-2020:7)	Nessus	Firewalls	8/27/2020	1/4/2021	high
144150	EulerOS 2.0 SP8 : squid (EulerOS-SA-2020-2534)	Nessus	Huawei Local Security Checks	12/14/2020	2/2/2024	high
148218	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Squid vulnerabilities (USN-4895-1)	Nessus	Ubuntu Local Security Checks	3/30/2021	9/3/2025	high

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