CVE-2007-6239: The "cache update reply processing" functionality in Squid 2.x before 2.6.STABLE17 and Squid 3.0 allows remote

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MEDIUM 5.0DOWNGRADE

CVE-2007-6239 is a medium-severity flaw (CVSS 5.0) affecting squid web proxy cache. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The "cache update reply processing" functionality in Squid 2.x before 2.6.STABLE17 and Squid 3.0 allows remote attackers to cause a denial of service (crash) via unknown vectors related to HTTP headers and an Array memory leak during requests for cached objects.

Why this priority

EPSS top 2%: very likely to be exploited
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	26.7% (top 2%)
CISA exploited list	No
Weakness	CWE-20
Published	2007-12-04
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: squid

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2007-12-04 18:46 UTCPublished CVE record published
2026-06-16 22:47 UTCUpdated Record last modified

squid squid web proxy cache DOWNGRADE

Affected: 2.0_patch2 · 2.1_patch2 · 2.3.stable4 · 2.3.stable5 · 2.4_stable2 · 2.4_stable4 · 2.4_stable6 · 2.4_stable7

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0_patch2

1. Check installed version

apt-cache policy squid-web-proxy-cache || rpm -q squid-web-proxy-cache || squid-web-proxy-cache --version

2. No fixed release: DOWNGRADE to a release before 2.0_patch2 (Debian / Ubuntu)

apt-cache madison squid-web-proxy-cache sudo apt install squid-web-proxy-cache=<VERSION_BEFORE_2.0_patch2> sudo apt-mark hold squid-web-proxy-cache

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list squid-web-proxy-cache sudo dnf downgrade squid-web-proxy-cache-<VERSION_BEFORE_2.0_patch2> sudo dnf versionlock add squid-web-proxy-cache

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2007-6239?

squid web proxy cache: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2007-6239 being exploited?

CVE-2007-6239 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-2007-6239 affect?

CVE-2007-6239 affects squid web proxy cache. Severity is medium (CVSS 5.0). The "cache update reply processing" functionality in Squid 2.x before 2.6.STABLE17 and Squid 3.0 allows remote attackers to cause a denial of service (crash) via unknown vectors related to HTTP headers and an Array memory leak during reques

How urgent is CVE-2007-6239?

Priority 47/100. EPSS top 2%: very likely to be exploited; Public exploit reference

Software pages

Squid vulnerabilities

Related CVEs

CVE-2009-0801 MEDIUM 5.4 DOWNGRADE Squid, when transparent interception mode is enabled, uses the HTTP Host header to determine the remote endpoi
CVE-2004-2480 MEDIUM 5.0 DOWNGRADE Squid Web Proxy Cache 2.3.STABLE5 allows remote attackers to bypass security controls and access arbitrary web
CVE-2004-2479 MEDIUM 5.0 DOWNGRADE Squid Web Proxy Cache 2.5 might allow remote attackers to obtain sensitive information via URLs containing inv
CVE-2004-0541 HIGH 10.0 DOWNGRADE Buffer overflow in the ntlm_check_auth (NTLM authentication) function for Squid Web Proxy Cache 2.5.x and 3.x,

References

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