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Servers and applications

CVE-2021-28651

SQUID-2021:1 Denial of Service in URN processing

Severity
High 7.5
Published
10 May 2021
Last changed
17 Jun 2026
Added to UpHeron
1 Nov 2026
Fixed in
4.15, 5.0.6
Also known as
GHSA-ch36-9jhx-phm4
Sources
NVD, Project advisories (GitHub)

Description

An issue was discovered in Squid before 4.15 and 5.x before 5.0.6. Due to a buffer-management bug, it allows a denial of service. When resolving a request with the urn: scheme, the parser leaks a small amount of memory. However, there is an unspecified attack methodology that can easily trigger a large amount of memory consumption.

Affected software

SoftwareAffected versions
SquidServers and applications · cpe:a:squid-cache:squid
  • From 2.0 before 4.15
  • From 5.0 before 5.0.6
SquidServers and applications · github:squid-cache/squid
  • From 5.0.1 before 5.0.6

References

  • NVD https://nvd.nist.gov/vuln/detail/CVE-2021-28651
  • CVE.org https://www.cve.org/CVERecord?id=CVE-2021-28651
  • GitHub Advisory Database https://github.com/advisories/GHSA-ch36-9jhx-phm4
  • github.com https://github.com/squid-cache/squid/security/advisories/GHSA-ch36-9jhx-phm4