TI-2023-26924 Aliases CVE-2023-49288

Denial of Service in HTTP Collapsed Forwarding in Squid

MEDIUM 51CWE-416Published 2023-12-04 · Updated 2025-02-13

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Partial Red Hat: 2 fixed, 2 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Affected versions of squid are subject to a a Use-After-Free bug which can lead to a Denial of Service attack via collapsed forwarding. All versions of Squid from 3.5 up to and including 5.9 configured with "collapsed_forwarding on" are vulnerable. Configurations with "collapsed_forwarding off" or without a "collapsed_forwarding" directive are not vulnerable. This bug is fixed by Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should remove all collapsed_forwarding lines from their squid.conf.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.04777 91st percentileScored 2026-11-07

Fix Partial squid (squid-cache): 6.0.1Red Hat: 2 advisoriesRed Hat: 2 fixed, 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
squid-cache	squid	3.5 to before 6.0.1	6.0.1	Patch available	CNA

squid Vendorsquid-cache Affected 3.5 to before 6.0.1 Fixed in 6.0.1 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:squid-cache:squid::::::::	3.5 – 5.9	Vulnerable	squid-cache

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* Versions 3.5 – 5.9 Vulnerable ·squid-cache

Remediation

Fix · CNA squid (squid-cache) Fixed in 6.0.1

Red Hat 2 advisories

RHSA-2023:7668 Released 2023-12-06 · Red Hat rating Important
squid:4 security update
- Red Hat Enterprise Linux AppStream (v. 8) libecap-1.0.1-2.module+el8.9.0+19703+a1da7223.aarch64::squid:4, libecap-1.0.1-2.module+el8.9.0+19703+a1da7223.ppc64le::squid:4, libecap-1.0.1-2.module+el8.9.0+19703+a1da7223.s390x::squid:4 +11
RHSA-2023:7465 Released 2023-11-22 · Red Hat rating Important
squid security update
- Red Hat Enterprise Linux AppStream (v. 9) squid-7:5.5-6.el9_3.2

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux 6	Affected	No fix planned: Out of support scope
Red Hat Enterprise Linux 7	Affected	No fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)	Fixed	RHSA-2023:7668
Red Hat Enterprise Linux AppStream (v. 9)	Fixed	RHSA-2023:7465

Timeline

2026-10-02 Threatist record created from CVE-2023-49288

References

Advisory 1

https://github.com/squid-cache/squid/security/advisories/GHSA-rj5h-46j6-q2g5

Other 3

TI-2025-38486 Squid vulnerable to information disclosure via authentication credential leakage in error handling CVSS 3.1CRITICAL 10.0
TI-2024-16845 Denial of Service in HTTP Header parser in squid proxy CVSS 3.1HIGH 7.5
TI-2024-16566 SQUID-2024:1 Denial of Service in HTTP Chunked Decoding CVSS 3.1HIGH 8.6
TI-2023-26921 Denial of Service in HTTP Message Processing in Squid CVSS 3.1HIGH 8.6
TI-2023-27496 SQUID-2023:10 Denial of Service in HTTP Request parsing CVSS 3.1HIGH 8.6
TI-2023-25306 Squid: denial of service in http digest authentication CVSS 3.1HIGH 8.6

See all 110 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences