CVE-2019-18677

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 7.2% 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-352

Description

An issue was discovered in Squid 3.x and 4.x through 4.8 when the append_domain setting is used (because the appended characters do not properly interact with hostname length restrictions). Due to incorrect message processing, it can inappropriately redirect traffic to origins it should not be delivered to.

Affected products

Canonical Ubuntu Linux: 16.04, 18.04, 19.04, 19.10
Fedoraproject Fedora: 30, 31
Squid: from 2.0 through 2.7; from 3.0 through 3.5.28; from 4.0 through 4.8; 2.7-stable2, 2.7-stable3, 2.7-stable4, 2.7-stable5, 2.7-stable6, 2.7-stable7 (+2)

References

http://www.squid-cache.org/Advisories/SQUID-2019_9.txt
http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-e5f1813a674848dde570f7920873e1071f96e0b4.patch
http://www.squid-cache.org/Versions/v4/changesets/squid-4-36492033ea4097821a4f7ff3ddcb971fbd1e8ba0.patch
https://bugzilla.suse.com/show_bug.cgi?id=1156328
https://github.com/squid-cache/squid/pull/427
https://lists.debian.org/debian-lts-announce/2019/12/msg00011.html
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://www.debian.org/security/2020/dsa-4682
http://www.squid-cache.org/Advisories/SQUID-2019_9.txt

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