squid-cache Squid up to 7.5 Header Parsing src/HttpHeader.cc request smuggling

Summaryinfo

A vulnerability labeled as problematic has been found in squid-cache Squid up to 7.5. The impacted element is an unknown function of the file src/HttpHeader.cc of the component Header Parsing. The manipulation results in request smuggling. This vulnerability was named CVE-2026-61642. The attack may be performed from remote. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic has been found in squid-cache Squid up to 7.5. Affected is an unknown part of the file src/HttpHeader.cc of the component Header Parsing. The manipulation with an unknown input leads to a request smuggling vulnerability. CWE is classifying the issue as CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. This is going to have an impact on integrity. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-61642 since 07/10/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/13/2026).

Upgrading to version 7.6 eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• squid-cache

Name

• Squid

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5

License

• open-source

Website

• Product: https://github.com/squid-cache/squid/

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