← Vulnerability feed

Vulnerability record · CVE-2023-49288 · published 4 December 2023

CVE-2023-49288: Squid-cache squid use after free vulnerability

Squid Cache · Squid

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.

7.5 CVSS 3.1 High EPSS 4.8% · top 8.4% CWE-416 · Use after free
7.5CVSS 3.1 base score
4.8%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/squid-cache/squid/security/advisories/GHSA-rj5h-46j6-q2g5 Vendor Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/A5QASTMCUSUEW3UOMKHZJB3FT
https://lists.fedoraproject.org/archives/list/[email protected]/message/MEV66D3PAAY6K7TWDT3WZBLCP
https://security.netapp.com/advisory/ntap-20240119-0006/
https://github.com/squid-cache/squid/security/advisories/GHSA-rj5h-46j6-q2g5 Vendor Advisory
https://lists.fedoraproject.org/archives/list/[email protected]/message/A5QASTMCUSUEW3UOMKHZJB3FT
https://lists.fedoraproject.org/archives/list/[email protected]/message/MEV66D3PAAY6K7TWDT3WZBLCP
https://security.netapp.com/advisory/ntap-20240119-0006/

Track CVE-2023-49288 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2025-54574Squid-cache squid heap-based buffer overflow vulnerabilitySquid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution att…EPSS 23%9.8CVE-2020-11945Squid-cache squid integer overflow vulnerabilityAn issue was discovered in Squid before 5.0.2. A remote attacker can replay a sniffed Digest Authentication nonce to gain access to resources that ar…EPSS 27%9.8CVE-2019-12519Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate. This function …EPSS 6.7%9.8CVE-2019-12524Squid-cache squid missing authentication for critical function vulnerabilityAn issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to see if the request should be denied. Squid…EPSS 4.3%9.8CVE-2019-12526Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid before 4.9. URN response handling in Squid suffers from a heap-based buffer overflow. When receiving data from a rem…EPSS 20%9.8CVE-2019-12525Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid 3.3.9 through 3.5.28 and 4.x through 4.7. When Squid is configured to use Digest authentication, it parses the heade…EPSS 24%9.2CVE-2026-33526Squid-cache squid use after free vulnerabilitySquid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP tr…EPSS 13%9.1CVE-2019-12523Squid-cache squid vulnerabilityAn issue was discovered in Squid before 4.9. When handling a URN request, a corresponding HTTP request is made. This HTTP request doesn't go through …EPSS 4.3%

Source: NIST National Vulnerability Database (record CVE-2023-49288), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.