Squid is a caching proxy for the Web. Prior to version 7.5, due to improper input validation, Squid is vulnerable to out of bounds read when handling ICP traffic. This problem allows a remote attacker to receive small amounts of memory potentially containing sensitive information when responding with errors to invalid ICP requests. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem cannot be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

An update of the squid package has been released.

The remote Debian 11 / 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4697 advisory.

    - -----------------------------------------------------------------------     Debian LTS Advisory DLA-4697-1              debian-lts@lists.debian.org     https://www.debian.org/lts/security/                      Utkarsh Gupta     July 24, 2026                               https://wiki.debian.org/LTS
    - -----------------------------------------------------------------------

    Package        : squid     Version        : 4.13-10+deb11u7 5.7-2+deb12u6     CVE ID         : CVE-2026-33515 CVE-2026-33526 CVE-2026-47729                      CVE-2026-50012

    Multiple security issues were discovered in the Squid proxy caching     server, which could result in information disclosure or denial of     service.

    For Debian 11 bullseye, these problems have been fixed in version     4.13-10+deb11u7.

    For Debian 12 bookworm, these problems have been fixed in version     5.7-2+deb12u6.

    We recommend that you upgrade your squid packages.

    For the detailed security status of squid please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/squid

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian 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 Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6360 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6360-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     June 21, 2026                         https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : squid     CVE ID         : CVE-2026-33515 CVE-2026-33526 CVE-2026-47729 CVE-2026-50012

    Multiple security issues were discovered in the Squid proxy caching     server, which could result in information disclosure or denial of service.

    For the stable distribution (trixie), these problems have been fixed in     version 6.13-2+deb13u2.

    We recommend that you upgrade your squid packages.

    For the detailed security status of squid please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/squid

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian 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 version of Tencent Linux installed on the remote TencentOS Server 4 host is prior to tested version. It is, therefore, affected by multiple vulnerabilities as referenced in the TSSA-2026:0346 advisory.

    Package updates are available for TencentOS Server 4 that fix the following vulnerabilities:

    CVE-2026-33526:
    Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is     vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to     perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol.
    This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero     `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version     7.5 contains a patch.

    CVE-2026-33515:
    Squid is a caching proxy for the Web. Prior to version 7.5, due to improper input validation, Squid is     vulnerable to out of bounds read when handling ICP traffic. This problem allows a remote attacker to     receive small amounts of memory potentially containing sensitive information when responding with errors     to invalid ICP requests. This attack is limited to Squid deployments that explicitly enable ICP support     (i.e. configure non-zero `icp_port`). This problem cannot be mitigated by denying ICP queries using     `icp_access` rules. Version 7.5 contains a patch.

    CVE-2026-32748:
    Squid is a caching proxy for the Web. Prior to version 7.5, due to premature release of resource during     expected lifetime and heap Use-After-Free bugs, Squid is vulnerable to Denial of Service when handling ICP     traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service     attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that     explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by     denying ICP queries using `icp_access` rules. This bug is fixed in Squid version 7.5.

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 Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-007175 advisory.

    Squid is a caching proxy for the Web. Prior to version 7.5, due to improper input validation, Squid is     vulnerable to out of bounds read when handling ICP traffic. This problem allows a remote attacker to     receive small amounts of memory potentially containing sensitive information when responding with errors     to invalid ICP requests. This attack is limited to Squid deployments that explicitly enable ICP support     (i.e. configure non-zero `icp_port`). This problem cannot be mitigated by denying ICP queries using     `icp_access` rules. Version 7.5 contains a patch.

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

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

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8157-1 advisory.

    It was discovered that Squid incorrectly handled certain ICP traffic. In environments where ICP support is     enabled, a remote attacker could use this issue to cause Squid to crash, resulting in a denial of service,     or obtain small amounts of sensitive information.

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.

The version of Squid on the remote host is prior to 7.5. It is, therefore, affected by multiple vulnerabilities:

  - Due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This attack is     limited to Squid deployments that explicitly enable ICP support. (CVE-2026-33526)

  - Due to improper input validation, Squid is vulnerable to out of bounds read when handling ICP traffic. This     allows a remote attacker to receive small amounts of memory potentially containing sensitive information.
    (CVE-2026-33515)

  - Due to premature release of resource during expected lifetime and heap Use-After-Free bugs, Squid is vulnerable     to Denial of Service when handling ICP traffic. (CVE-2026-32748)

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

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

  - Squid is a caching proxy for the Web. Prior to version 7.5, due to improper input validation, Squid is     vulnerable to out of bounds read when handling ICP traffic. This problem allows a remote attacker to     receive small amounts of memory potentially containing sensitive information when responding with errors     to invalid ICP requests. This attack is limited to Squid deployments that explicitly enable ICP support     (i.e. configure non-zero `icp_port`). This problem cannot be mitigated by denying ICP queries using     `icp_access` rules. Version 7.5 contains a patch. (CVE-2026-33515)

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

ID	Name	Product	Family	Type	Severity
333889	Photon OS 5.0: Squid PHSA-2026-5.0-91-0819	Nessus	PhotonOS Local Security Checks	Local	critical
329264	Debian dla-4697 : squid - security update	Nessus	Debian Local Security Checks	Local	critical
321872	Debian dsa-6360 : squid - security update	Nessus	Debian Local Security Checks	Local	critical
318558	TencentOS Server 4: squid (TSSA-2026:0346)	Nessus	Tencent Local Security Checks	Local	critical
306998	Photon OS 5.0: Squid PHSA-2026-5.0-0819	Nessus	PhotonOS Local Security Checks	Local	critical
306994	Photon OS 4.0: Squid PHSA-2026-4.0-0996	Nessus	PhotonOS Local Security Checks	Local	critical
306831	Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: squid (UTSA-2026-007175)	Nessus	Unity Linux Local Security Checks	Local	medium
306089	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 : Squid vulnerabilities (USN-8157-1)	Nessus	Ubuntu Local Security Checks	Local	critical
303933	Squid < 7.5 Multiple Vulnerabilities	Nessus	Firewalls	Remote	critical
303662	Linux Distros Unpatched Vulnerability : CVE-2026-33515	Nessus	Misc.	Local	medium

Detections

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CVE-2026-33515

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Tenable Plugins

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