CVE-2019-18676

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 9.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2019-11-26 · updated 2026-06-17
Weakness: CWE-787

Description

An issue was discovered in Squid 3.x and 4.x through 4.8. Due to incorrect input validation, there is a heap-based buffer overflow that can result in Denial of Service to all clients using the proxy. Severity is high due to this vulnerability occurring before normal security checks; any remote client that can reach the proxy port can trivially perform the attack via a crafted URI scheme.

Affected products

Canonical Ubuntu Linux: 16.04, 18.04, 19.04, 19.10
Debian Linux: 9.0, 10.0
Fedoraproject Fedora: 30, 31
Squid: from 3.0 through 3.5.28; from 4.0 through 4.8

References

http://www.squid-cache.org/Advisories/SQUID-2019_8.txt
http://www.squid-cache.org/Versions/v4/changesets/squid-4-fbbdf75efd7a5cc244b4886a9d42ea458c5a3a73.patch
https://bugzilla.suse.com/show_bug.cgi?id=1156329
https://github.com/squid-cache/squid/pull/275
https://lists.debian.org/debian-lts-announce/2020/07/msg00009.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MTM74TU2BSLT5B3H4F3UDW53672NVLMC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UEMOYTMCCFWK5NOXSXEIH5D2VGWVXR67/
https://usn.ubuntu.com/4213-1/
https://usn.ubuntu.com/4446-1/
https://www.debian.org/security/2020/dsa-4682
http://www.squid-cache.org/Advisories/SQUID-2019_8.txt
http://www.squid-cache.org/Versions/v4/changesets/squid-4-fbbdf75efd7a5cc244b4886a9d42ea458c5a3a73.patch

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