[squid-announce] [ADVISORY] SQUID-2026:9 FTP command injection in FTP gateway

[Amos Jeffries]

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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 <squid-users at 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 at 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.

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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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