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Published: 26 November 2019

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.



CVSS 3 base score: 5.3


Package Release Status
Launchpad, Ubuntu, Debian
Released (4.9-1)
Ubuntu 21.04 (Hirsute Hippo)
Released (4.9-2ubuntu1)
Ubuntu 20.04 LTS (Focal Fossa)
Released (4.9-2ubuntu1)
Ubuntu 18.04 LTS (Bionic Beaver) Does not exist

Ubuntu 16.04 ESM (Xenial Xerus) Does not exist

Ubuntu 14.04 ESM (Trusty Tahr) Does not exist

Launchpad, Ubuntu, Debian
Upstream Needs triage

Ubuntu 21.04 (Hirsute Hippo) Does not exist

Ubuntu 20.04 LTS (Focal Fossa) Does not exist

Ubuntu 18.04 LTS (Bionic Beaver)
Released (3.5.27-1ubuntu1.4)
Ubuntu 16.04 ESM (Xenial Xerus)
Released (3.5.12-1ubuntu7.9)
Ubuntu 14.04 ESM (Trusty Tahr) Does not exist