Headline
CVE-2023-49288: SQUID-2023:9 Denial of Service in HTTP Collapsed Forwarding
Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Affected versions of squid are subject to a a Use-After-Free bug which can lead to a Denial of Service attack via collapsed forwarding. All versions of Squid from 3.5 up to and including 5.9 configured with “collapsed_forwarding on” are vulnerable. Configurations with “collapsed_forwarding off” or without a “collapsed_forwarding” directive are not vulnerable. This bug is fixed by Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should remove all collapsed_forwarding lines from their squid.conf.
Due to a Use-After-Free bug Squid is vulnerable to a Denial of
Service attack against collapsed forwarding
Severity:
This problem allows a remote client to perform Denial of
Service attack on demand when Squid is configured with collapsed
forwarding.
CVSS Score of 8.6
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H&version=3.1
Updated Packages:****This bug is fixed by Squid version 6.0.1.
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:
Run the following command to identify how (and whether)
your Squid has been configured with collapsed forwarding:
`squid -k parse 2>&1 | grep collapsed_forwarding`
All Squid-3.5 up to and including 5.9 configured with
“collapsed_forwarding on” are vulnerable.
All Squid-3.5 up to and including 5.9 configured with
“collapsed_forwarding off” are not vulnerable.
All Squid-3.5 up to and including 5.9 configured without any
“collapsed_forwarding” directive are not vulnerable.
Workaround:
Remove all collapsed_forwarding lines from your squid.conf.
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
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
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 Joshua Rogers of Opera
Software.
Fixed by The Measurement Factory.
Revision history:
2022-09-03 18:41:32 UTC Patches Released
2023-10-12 11:53:02 UTC Initial Report
END
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Ubuntu Security Notice 6728-1 - Joshua Rogers discovered that Squid incorrectly handled collapsed forwarding. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service. This issue only affected Ubuntu 20.04 LTS and Ubuntu 22.04 LTS. Joshua Rogers discovered that Squid incorrectly handled certain structural elements. A remote attacker could possibly use this issue to cause Squid to crash, resulting in a denial of service.