Use After Free in Squid - CVE-2026-33526

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Main Vulnerability Database Vulnerabilities #VU124610

Use After Free in Squid - CVE-2026-33526

Published: March 25, 2026


Vulnerability identifier: #VU124610
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-33526
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to heap use-after-free in ICP request handling when processing ICP traffic. A remote attacker can send a specially crafted ICP request to cause a denial of service.

The attack is limited to Squid deployments that have ICP support enabled via a non-zero icp_port configuration.


Affected software

Squid
SUSE Linux Enterprise Server 15 SP6
Debian Linux
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for ARM 64
Anolis OS
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux Server - TUS
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Server Applications Module
openSUSE Leap
openEuler
Ubuntu
Fedora
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
libecap-devel
libecap
squid
squid-debuginfo
squid-debugsource
squid (Red Hat package)
squid (Ubuntu package)
squid (Debian package)

How to mitigate CVE-2026-33526

Install security update from vendor's website.

Squid - update to 7.5
libecap-devel - update to 1.0.1-2.0.1
libecap - update to 1.0.1-2.0.1
squid - addressed in versions 4.9-26, 4.9-30, 6.6-8
squid-debuginfo - addressed in versions 4.9-26, 4.9-30, 6.6-8
squid-debugsource - addressed in versions 4.9-26, 4.9-30, 6.6-8
squid - update to 4.15-13
squid (Red Hat package) - addressed in versions 5.2-1.el9_0.10, 5.5-5.el9_2.11, 5.5-19.el9_6.3, 5.5-22.el9_7.4, 6.10-5.el10_0.2
squid-debugsource - update to 6.14-150600.3.20.1
squid-debuginfo - update to 6.14-150600.3.20.1
squid - update to 6.14-150600.3.20.1
squid - addressed in versions 7.5-1.fc43, 7.5-1.fc44
squid (Ubuntu package) - addressed in versions 5.9-0ubuntu0.22.04.5, 6.14-0ubuntu0.24.04.2, 6.14-0ubuntu0.25.10.2
squid (Debian package) - update to 6.13-2+deb13u2

External References

Related Security Bulletins