The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 16.04 LTS / 18.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4446-1 advisory.

    Jeriko One discovered that Squid incorrectly handled caching certain requests. A remote attacker could     possibly use this issue to perform cache-injection attacks or gain access to reverse proxy features such     as ESI. (CVE-2019-12520)

    Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly handled certain URN requests. A     remote attacker could possibly use this issue to bypass access checks. (CVE-2019-12523)

    Jeriko One discovered that Squid incorrectly handled URL decoding. A remote attacker could possibly use     this issue to bypass certain rule checks. (CVE-2019-12524)

    Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly handled input validation. A remote     attacker could use this issue to cause Squid to crash, resulting in a denial of service. (CVE-2019-18676)

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.

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 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     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 4.10. 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)

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 Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALINUX3-SA-2022:0124 advisory.

    Package updates are available for Alibaba Cloud Linux 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 Alibaba Cloud 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.

ID	Name	Product	Family	Published	Updated	Severity
222573	Linux Distros Unpatched Vulnerability : CVE-2019-12524	Nessus	Misc.	3/4/2025	8/20/2025	critical
139313	Ubuntu 16.04 LTS / 18.04 LTS : Squid vulnerabilities (USN-4446-1)	Nessus	Ubuntu Local Security Checks	8/4/2020	8/27/2024	critical
139987	EulerOS 2.0 SP8 : squid (EulerOS-SA-2020-1884)	Nessus	Huawei Local Security Checks	8/28/2020	2/22/2024	critical
236441	Alibaba Cloud Linux 3 : 0124: squid:4 (ALINUX3-SA-2022:0124)	Nessus	Alibaba Cloud Linux Local Security Checks	5/14/2025	5/14/2025	critical

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