CVE-2023-49288

Denial of Service in HTTP Collapsed Forwarding in Squid

HIGH
7.5
CVSS Score
Published: December 4, 2023 at 10:49 PM UTC
Updated: June 17, 2026 at 06:35 AM UTC
2 products affected across 1 vendorSquidCache Squid

Using squid by squid-cache?

Get instant alerts when new vulnerabilities affect squid - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
HIGH7.5
Exploit prediction
EPSS 5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 6.0.13.5 ≤ v ≤ 5.9
Affected range stops below 6.0.1, so it looks safe — our inference, not a vendor statement
v < 6.0.13.5 ≤ v ≤ 5.9
Affected range stops below 6.0.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-416

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card