What’s Vulnerable › Vulnerabilities

CVE-2019-18678

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 6.2% 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-444

Description

An issue was discovered in Squid 3.x and 4.x through 4.8. It allows attackers to smuggle HTTP requests through frontend software to a Squid instance that splits the HTTP Request pipeline differently. The resulting Response messages corrupt caches (between a client and Squid) with attacker-controlled content at arbitrary URLs. Effects are isolated to software between the attacker client and Squid. There are no effects on Squid itself, nor on any upstream servers. The issue is related to a request header containing whitespace between a header name and a colon.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 19.04, 19.10
• Debian Linux: 8.0
• 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_10.txt
• http://www.squid-cache.org/Versions/v4/changesets/squid-4-671ba97abe929156dc4c717ee52ad22fba0f7443.patch
• https://bugzilla.suse.com/show_bug.cgi?id=1156323
• https://github.com/squid-cache/squid/pull/445
• 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://security.gentoo.org/glsa/202003-34
• https://usn.ubuntu.com/4213-1/
• https://www.debian.org/security/2020/dsa-4682
• http://www.squid-cache.org/Advisories/SQUID-2019_10.txt

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