Denial of Service in HTTP Collapsed Forwarding in Squid (squid-cache squid)

CVE-2023-49288

HIGH 8.6

At a glance

Source: NVD
EPSS: EPSS 4.78 % · percentile 92 (2026-10-31)
State: PUBLISHED
Published: 2023-12-04 22:49 UTC
Updated: 2025-02-13 17:18 UTC
Assigner: GitHub_M
NVD status: Modified

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Description

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.

Weaknesses (CWE)

CWE-416 — Use After Free

References

Scores

Version	Score	Vector	Scored by
CVSS 3.1	HIGH 8.6	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H	GitHub_M
CVSS 3.1	HIGH 8.6	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H	NVD · security-advisories@github.com (Secondary)
CVSS 3.1	HIGH 7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	NVD · nvd@nist.gov (Primary)

European references

ENISA EUVD · EUVD-2023-53281
GCVE · GCVE-0-2023-49288

Affected configurations (NVD CPE)

cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:* ≥ 3.5 ≤ 5.9

Affected products

Product	Versions
squid-cache · squid	affected >= 3.5, < 6.0.1

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD

⚠️ Denial of Service in HTTP Collapsed Forwarding in Squid (squid-cache squid)