CVE-2004-0541: Buffer overflow in the ntlm_check_auth (NTLM authentication) function for Squid Web Proxy Cache 2.5.x and 3.x,

This week

HIGH 10.0DOWNGRADE

CVE-2004-0541 is a high-severity flaw (CVSS 10.0) affecting squid web proxy cache. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Buffer overflow in the ntlm_check_auth (NTLM authentication) function for Squid Web Proxy Cache 2.5.x and 3.x, when compiled with NTLM handlers enabled, allows remote attackers to execute arbitrary code via a long password ("pass" variable).

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Public exploit reference

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

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	71.1% (top 1%)
CISA exploited list	No
Published	2004-08-06
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: national science foundation

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

Am I affected?

Timeline

2004-08-06 04:00 UTCPublished CVE record published
2026-06-16 22:05 UTCUpdated Record last modified

national science foundation squid web proxy cache DOWNGRADE

Affected: 2.5_stable · 3_pre

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.5_stable

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 2.5_stable (Debian / Ubuntu)

apt-cache madison squid-web-proxy-cache sudo apt install squid-web-proxy-cache=<VERSION_BEFORE_2.5_stable> 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_2.5_stable> 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.

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Exploit-DB: Squid - NTLM (Authenticated) Overflow (Metasploit)
Exploit-DB: Squid 2.5.x/3.x - NTLM Buffer Overflow (Metasploit)
Metasploit: Squid NTLM Authenticate Overflow

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-2004-0541?

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

Is CVE-2004-0541 being exploited?

CVE-2004-0541 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-2004-0541 affect?

CVE-2004-0541 affects squid web proxy cache. Severity is high (CVSS 10.0). Buffer overflow in the ntlm_check_auth (NTLM authentication) function for Squid Web Proxy Cache 2.5.x and 3.x, when compiled with NTLM handlers enabled, allows remote attackers to execute arbitrary code via a long password ("pass" variable)

How urgent is CVE-2004-0541?

Priority 65/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference

Software pages

Squid vulnerabilities

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References

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