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SQUID-2025:1 Buffer Overflow in URN Handling

Critical
yadij published GHSA-w4gv-vw3f-29g3 Jul 31, 2025

Package

squid (Squid)

Affected versions

<6.4

Patched versions

6.4

Description

Due to incorrect buffer management Squid is vulnerable to a
heap buffer overflow and possible remote code execution attack
when processing URN.

Severity:

This problem allows a remote server to perform a Buffer Overflow
attack when delivering URN Trivial-HTTP responses. Potentially
allowing delivery of up to 4KB of Squid allocated heap memory
to the client.

Revealed memory may include security credentials or other
confidential data.

Updated Packages:

This bug is fixed by Squid version 6.4.

In addition, patches addressing this problem for the stable
releases can be found in our patch archives:

Squid 6:

a27bf4b

If you are using a prepackaged version of Squid then please refer
to the package vendor for availability information on updated
packages.

Determining if your version is vulnerable:

Squid older than 4.14 have not been tested and should be assumed
to be vulnerable.

All Squid-4.x up to and including 4.17 are vulnerable.

All Squid-5.x up to and including 5.9 are vulnerable.

All Squid-6.x up to and including 6.3 are vulnerable.

Workaround:

Disable URN access permissions.

acl URN proto URN
http_access deny URN

Contact details for the Squid project:

For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
package vendor.

If you install and build Squid from the original Squid sources
then the [email protected] mailing list is your
primary support point. For subscription details see
http://www.squid-cache.org/Support/mailing-lists.html.

For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
https://bugs.squid-cache.org/.

For reporting of security sensitive bugs send an email to the
[email protected] mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.

Credits:

This vulnerability was discovered by StarryNight.

Fixed by The Measurement Factory.

Revision history:

2023-06-24 08:18:55 UTC Fix published
2025-07-01 18:40:24 UTC Initial Report

END

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:H

CVE ID

CVE-2025-54574

Weaknesses

Heap-based Buffer Overflow

A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Learn more on MITRE.