VulnerabilityAwaiting Analysis

CVE-2026-61642

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.

HIGH 7.7EPSS 2.22%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (2.22%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 3.1: 7.7 HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:H/A:N
EPSS: 2.22% probability · 83th percentile
Public exploits: None in Exploit-DB
CISA KEV: Not listed
Weakness: CWE-444
Source: security-advisories@github.com

EPSS trend

EPSS moved from 4.7% on 14 October 2026 to 2.2% on 26 October 2026.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.