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Squid Proxy Cache Security Update Advisory SQUID-2026:9
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Advisory ID: | SQUID-2026:9
Date: | 2026-07-05
Summary: | FTP command injection in FTP gateway
Affected versions: | Squid 2.x -> 2.7.STABLE9
| Squid 3.x -> 3.5.28
| Squid 4.x -> 4.17
| Squid 5.x -> 5.9
| Squid 6.x -> 6.14
| Squid 7.x -> 7.6
Fixed in version: | Squid 7.7
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Problem Description:
Due to a Improper Validation of Syntactic Correctness
bug Squid is vulnerable to a Command Injection
attack against FTP Gateway.
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Severity:
This problem allows a trusted client to perform Command
Injection when accessing an ftp:// URL. Allowing the client
access to files, directories and features of the FTP server
normally forbidden by Squid security policy.
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Updated Packages:
This bug is fixed by Squid version 7.7.
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/523ed3b037cd61b9e3222a6c5d937728fb21aeee.patch>
If you are using a prepackaged version of Squid then please
refer to the package vendor for availability information on
updated packages.
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Determining if your version is vulnerable:
Squid older than 5.0 have not been tested and should be
assumed to be vulnerable.
All Squid-5.x up to and including 5.9 are vulnerable.
All Squid-6.x up to and including 6.14 are vulnerable.
All Squid-7.x up to and including 7.6 are vulnerable.
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Workaround:
Forbid access to FTP Gateway by placing the below settings
before any "http_access allow" lines in squid.conf:
acl FTP proto FTP
http_access deny FTP
Also, remove from squid.conf the line:
acl Safe_ports port 21
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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
<http://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.
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Credits:
This vulnerability was discovered independently by
David Fifield, and
Pavel Kohout of Aisle Research, and
Ajith Prabhu
Fixed by Ricardo Ferreira Ribeiro of Open Systems AG
in collaboration with The Measurement Factory.
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Revision history:
2019-06-21 00:00:52 UTC Initial Report by David Fifield
2026-03-02 19:38:00 UTC Report by Ajith Prabhu
2026-03-04 12:41:54 UTC Report by Pavel Kohout of Aisle Research
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END
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