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CVE-2026-33526: Squid is a caching proxy for the Web

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This week
HIGH 7.5REMOTEUPGRADE

CVE-2026-33526 is a high-severity flaw (CVSS 7.5) affecting squid. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 mitiga

Why this priority

  • High severity
  • EPSS top 5%: very likely to be exploited
  • Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance9.1% (top 5%)
CISA exploited listNo
WeaknessCWE-416, CWE-826, CWE-825
Published2026-03-26
Last modified2026-07-15
Publisher (CNA): GitHub, Inc. · Vendor: squid-cache

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Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

squid-cache squid UPGRADE
Affected: < 7.5
Fixed in: 7.5
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy squid || rpm -q squid || squid --version
2. UPGRADE to 7.5 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade squid
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade squid
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Exact fixes by distribution

Fedora ELN · perl-Encode · FIXED · 3.25-528.eln159 · FEDORA-2026-79991d0238 · source
sudo dnf upgrade --advisory=FEDORA-2026-79991d0238
Fedora 46 · fonttools · FIXED · 4.68.0-1.fc46 · FEDORA-2026-65d6c01c75 · source
sudo dnf upgrade --advisory=FEDORA-2026-65d6c01c75
Ubuntu 20.04 · squid · FIXED · 4.10-1ubuntu1.13+esm3
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "4.10-1ubuntu1.13+esm3" && echo PATCHED || echo STILL-VULNERABLE
Ubuntu 22.04 · squid · FIXED · 5.9-0ubuntu0.22.04.5
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "5.9-0ubuntu0.22.04.5" && echo PATCHED || echo STILL-VULNERABLE
Ubuntu 24.04 · squid · FIXED · 6.14-0ubuntu0.24.04.2
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "6.14-0ubuntu0.24.04.2" && echo PATCHED || echo STILL-VULNERABLE
Ubuntu 25.10 · squid · FIXED · 6.14-0ubuntu0.25.10.2
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "6.14-0ubuntu0.25.10.2" && echo PATCHED || echo STILL-VULNERABLE
Debian 12 · squid · FIXED · 5.7-2+deb12u6
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "5.7-2+deb12u6" && echo PATCHED || echo STILL-VULNERABLE
Debian 13 · squid · FIXED · 6.13-2+deb13u2
sudo apt update && sudo apt install --only-upgrade squid dpkg --compare-versions "$(dpkg-query -W -f='${Version}' squid)" ge "6.13-2+deb13u2" && echo PATCHED || echo STILL-VULNERABLE
RHEL 10 · squid · FIXED · squid-6.10-6.el10_1.3
sudo dnf upgrade --advisory=RHSA-2026:8119 rpm -q squid
RHEL 10.0 Extended Update Support · squid · FIXED · squid-6.10-5.el10_0.2
sudo dnf upgrade --advisory=RHSA-2026:11901 rpm -q squid
RHEL 7 Extended Lifecycle Support · squid · FIXED · squid-3.5.20-17.el7_9.16
sudo dnf upgrade --advisory=RHSA-2026:8880 rpm -q squid
RHEL 9 · squid · FIXED · squid-5.5-22.el9_7.4
sudo dnf upgrade --advisory=RHSA-2026:6301 rpm -q squid
RHEL 9.0 Update Services for SAP Solutions · squid · FIXED · squid-5.2-1.el9_0.10
sudo dnf upgrade --advisory=RHSA-2026:10256 rpm -q squid
Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1569 · source
sudo dnf update --advisory=ALAS2023-2026-1569
Amazon Linux 2 · see advisory · FIXED · ALAS2-2026-3242 · source
sudo yum update --advisory=ALAS2-2026-3242
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33526?

squid: upgrade to 7.5. Exact commands for each OS are on this page.

Is CVE-2026-33526 being exploited?

CVE-2026-33526 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33526 affect?

CVE-2026-33526 affects squid. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-33526?

Priority 55/100. High severity; EPSS top 5%: very likely to be exploited; Remotely exploitable, no login, no user action

Software pages

Squid vulnerabilities

Related CVEs

References

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