Problem Description:

Due to incorrect input validation Squid is vulnerable to a Request Smuggling and
Poisoning attack against the HTTP cache.

Severity:

This problem allows a trusted client to perform request smuggling and poison the
HTTP cache contents with crafted HTTP(S) request messages.

This attack requires an upstream server to participate in the smuggling and
generate the poison response sequence. Most popular server software are not
vulnerable to participation in this attack.

CVSS Score of 9.3
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:F/RL:O/RC:C/CR:H/IR:H/AR:H/MAV:N/MAC:L/MPR:L/MUI:N/MS:C/MC:H/MI:H/MA:H&version=3.1

Updated Packages:

This bug is fixed by Squid versions 4.12 and 5.0.3.

In addition, patches addressing this problem for the stable
releases can be found in our patch archives:

Squid 4:

http://www.squid-cache.org/Versions/v4/SQUID-2020_7.patch

Squid 5:

http://www.squid-cache.org/Versions/v5/SQUID-2020_7.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:

All Squid-2.x up to and including 2.7.STABLE9 are vulnerable.

All Squid-3.x up to and including 3.5.28 are vulnerable.

All Squid-4.x up to and including 4.11 are vulnerable.

Squid-5.0.1 and 5.0.2 are vulnerable.

Workaround:

There is no workaround for this vulnerability.

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 squid-users@lists.squid-cache.org mailing list is your
primary support point. For subscription details see
http://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
http://bugs.squid-cache.org/.

For reporting of security sensitive bugs send an email to the
squid-bugs@lists.squid-cache.org 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 Alex Rousskov of The Measurement Factory.

Independent discovery and replication reported by Amit Klein of Safebreach.

Fixed by Alex Rousskov of The Measurement Factory.

Revision history:

2016-09-06 02:45:20 UTC Initial Report
2020-05-11 12:41:17 UTC Replication Reported
2020-05-13 14:05:00 UTC Patch Released
2020-06-25 11:15:10 UTC CVE Allocated