OESA-2026-4582: squid security update
Squid is a high-performance proxy caching server. It handles all requests in a single, non-blocking, I/O-driven process and keeps meta data and implements negative caching of failed requests. Security Fix(es):
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.(CVE-2026-61642)
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
openeuler/squidto a version that resolves this vulnerability.Fixed in 6.6-10.oe2403sp1 - Upgrade
Upgrade
Squidto a version that resolves this vulnerability.Fixed in 7.6
Event History
Frequently Asked Questions
What conditions are required for exploitation?
An attacker must be a trusted client able to send HTTP/1.1 requests through the affected Squid instance. The issue involves acceptance of a prohibited bare "Transfer-Encoding: identity" header form.
Which deployments face the greatest downstream impact?
Deployments with an HTTP cache operating before the affected Squid are at risk of cache poisoning. An attacker may store arbitrary malicious content at any URL, which can then be served to other clients making later requests.
What version resolves the issue?
The issue is fixed in Squid version 7.6. Versions from 3.3.0.1 up to, but not including, 7.6 are affected.