Vulnerability · Published Oct 13, 2026 · Assigned by GitHub_M
CVE-2026-61642Squid Request Smuggling in HTTP Transfer-Encoding
High 7.7
In plain English
A high-severity security flaw in squid from squid-cache. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 2.0% (higher than 81% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Squid is a caching proxy for the Web. From 3.3.0.1 to before 7.6, due to an improper enforcement of behavioral workflow bug, Squid is vulnerable to a Request Smuggling attack against HTTP/1.1 Transfer-Encoding. HTTP header parsing (`src/HttpHeader.cc`) accepted the bare` Transfer-Encoding:` identity form, which the HTTP specification prohibits because any transfer coding must be wrapped within chunked encoding. This problem allows a trusted client to perform an HTTP Request Smuggling attack when HTTP/1.1 is used, bypassing security mechanisms that may be in place between attacker and Squid. When there is an HTTP cache operating prior to the affected Squid, this Request Smuggling attack also allows the attacker to poison that web cache and store arbitrary malicious content at any URL for delivery to other clients' future requests. This issue is fixed in version 7.6.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | squid | no fix listed | DEBIAN-CVE-2026-61642 |
| Debian:13 | squid | 6.13-2+deb13u4 | DEBIAN-CVE-2026-61642 |
| Debian:14 | squid | 7.6-1 | DEBIAN-CVE-2026-61642 |
| Ubuntu:22.04:LTS | squid | 5.9-0ubuntu0.22.04.8 | UBUNTU-CVE-2026-61642 |
| Ubuntu:22.04:LTS | squid | 5.9-0ubuntu0.22.04.8 | USN-8941-1 |
| Ubuntu:24.04:LTS | squid | 6.14-0ubuntu0.24.04.5 | USN-8941-1 |
| Ubuntu:24.04:LTS | squid | 6.14-0ubuntu0.24.04.5 | UBUNTU-CVE-2026-61642 |
| Ubuntu:26.04:LTS | squid | 7.7-0ubuntu0.26.04.2 | USN-8998-1 |
| Ubuntu:26.04:LTS | squid | 7.7-0ubuntu0.26.04.2 | UBUNTU-CVE-2026-61642 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| squid-cache | squid | >= 3.3.0.1, < 7.6 |
Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
References
- https://github.com/squid-cache/squid/security/advisories/GHSA-537g-4gfh-w7m6 x_refsource_CONFIRM
- https://github.com/squid-cache/squid/pull/2427 x_refsource_MISC
- https://github.com/squid-cache/squid/pull/2431 x_refsource_MISC
- https://github.com/squid-cache/squid/commit/d06f48de8b8cc9a378cb91ecfe8e89b6e81696d2 x_refsource_MISC
- https://github.com/squid-cache/squid/commit/d808a7c825a70275113790471135c9c4d547ee51 x_refsource_MISC
- https://github.com/squid-cache/squid/releases/tag/SQUID_7_6 x_refsource_MISC