CVE-2026-61642 Squid Request Smuggling in HTTP Transfer-Encoding
Attackers can smuggle HTTP requests to bypass security controls and poison web caches, affecting Squid proxy deployments.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-61642?
CVE-2026-61642 is a high-severity vulnerability in squid-cache squid, published on 13 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
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.
Weakness: CWE-444
Which versions are affected by CVE-2026-61642?
How do I fix CVE-2026-61642?
Upgrade to a fixed version.
Is CVE-2026-61642 being exploited?
There is no known exploitation of CVE-2026-61642 in the wild and no public exploit code.
Sources
Also known as AZL-108531, CLSA-2026-1792505835, CLSA-2026-1792517219, CLSA-2026-1792806435, DEBIAN-CVE-2026-61642, GHSA-537g-4gfh-w7m6 and 5 more.