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VulnerabilityPublished Updated

CVE-2025-54574: squid · Heap-based Buffer Overflow

Affects squidSource CVE Database V5

0

Not known to be exploited · 23% EPSS · CVSS 9.3 Critical : upgrade to 6.4 as a priority.

Data as of 27 Oct 2026, 05:11 UTC

CVSS 3.1 base score
9.3Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
23.9% chance of exploitation in 30 days – higher than 97% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 6.4
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Aug 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade squid to 6.4.

Affected software

ProductAffectedFixed in
squid-cache squidAffected
  • <6.4
Fixed in
  • 6.4

AI-suggested

European organizations should immediately upgrade all Squid proxy servers to version 6.4 or later to fully remediate the vulnerability. Where immediate patching is not feasible, administrators should disable URN access permissions as a temporary workaround to mitigate exploitation risk. Network segmentation should be enforced to limit access to proxy servers from untrusted networks. Implement strict ingress filtering and monitor network traffic for unusual URN requests or anomalies indicative of exploitation attempts. Employ host-based intrusion detection systems (HIDS) and endpoint protection solutions to detect potential memory corruption or code execution attempts. Regularly audit proxy configurations and logs to identify suspicious activity. Additionally, organizations should maintain an up-to-date inventory of Squid deployments and ensure timely application of security updates. Security teams should prepare incident response plans specific to proxy compromise scenarios and conduct threat hunting exercises focused on this vulnerability. Collaboration with ISPs and CERTs in Europe can aid in early detection of emerging exploit campaigns.

Description

Squid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution attack when processing URN due to incorrect buffer management. This has been fixed in version 6.4. To work around this issue, disable URN access permissions.

References

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