__________________________________________________________________
Squid Proxy Cache Security Update Advisory SQUID-2026:6
__________________________________________________________________
Advisory ID: | SQUID-2026:6
Date: | 2026-06-23
Summary: | Request Smuggling in HTTP Transfer-Encoding
Affected versions: | Squid 3.3 -> 3.5.28
| Squid 4.x -> 4.17
| Squid 5.x -> 5.9
| Squid 6.x -> 6.14
| Squid 7.x -> 7.5
Fixed in version: | Squid 7.6
__________________________________________________________________
Problem Description:
Due to a CWE-841 Improper Enforcement of Behavioral Workflow
bug Squid is vulnerable to a Request Smuggling attack against
HTTP/1.1 Transfer-Encoding.
__________________________________________________________________
Severity:
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.
__________________________________________________________________
Updated Packages:
This bug is fixed by Squid version 7.6.
In addition, patches addressing this problem for the stable
releases can be found in our patch archives:
Squid 7:
<https://github.com/squid-cache/squid/commit/d06f48de8b8cc9a378cb91ecfe8e89b6e81696d2.patch>
If you are using a prepackaged version of Squid then please
refer to the package vendor for availability information on
updated packages.
__________________________________________________________________
Determining if your version is vulnerable:
Squid older than 3.3 have not been tested and should be
assumed to be not vulnerable.
All Squid-3.3 up to and including 3.5.28 have not been tested
and should be assumed to be vulnerable.
All Squid-4.x up to and including 4.17 have not been tested
and should be assumed to be vulnerable.
All Squid-5.x up to and including 5.9 have not been tested
and should be assumed to be vulnerable.
All Squid-6.x up to and including 6.14 are vulnerable.
All Squid-7.x up to and including 7.5 are vulnerable.
__________________________________________________________________
Workaround:
There is no workaround for these issues.
__________________________________________________________________
Contact details for the Squid project:
For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
package vendor.
If you install and build Squid from the original Squid sources
then the <[email protected]> mailing list is
your primary support point. For subscription details see
<https://www.squid-cache.org/Support/mailing-lists.html>.
For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
<https://bugs.squid-cache.org/>.
For reporting of security sensitive bugs send an email to the
<[email protected]> mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.
__________________________________________________________________
Credits:
This vulnerability was discovered by
Mitchell Benjamin, Revamp Studio.
Fixed by Amos Jeffries , Treehouse Networks Ltd.
__________________________________________________________________
Revision history:
2026-05-29 08:04:59 UTC Initial Report
2026-05-31 08:29:04 UTC Patch Released
__________________________________________________________________
END
_______________________________________________
squid-announce mailing list
[email protected]
https://lists.squid-cache.org/listinfo/squid-announce
