[squid-announce] [ADVISORY] SQUID-2023:1 Request/Response smuggling in HTTP(S) and ICAP

Amos Jeffries squid3 at treenet.co.nz
Sat Oct 21 19:50:03 UTC 2023


Squid Proxy Cache Security Update Advisory SQUID-2023:1

Advisory ID:       | SQUID-2023:1
Date:              | October 22, 2023
Summary:           | Request/Response smuggling in HTTP(S) and ICAP
Affected versions: | Squid 2.6.STABLE10  -> 2.7.STABLE9
                    | Squid 3.x -> 3.5.28
                    | Squid 4.x -> 4.16
                    | Squid 5.x -> 5.9
                    | Squid 6.x -> 6.3
Fixed in version:  | Squid 6.4

Problem Description:

  Due to chunked decoder lenience Squid is vulnerable to
  Request/Response smuggling attacks when parsing HTTP/1.1
  and ICAP messages.



  This problem allows a remote attacker to perform
  Request/Response smuggling past firewall and frontend security
  systems when the upstream server interprets the chunked encoding
  syntax differently from Squid.

  This attack is limited to the HTTP/1.1 and ICAP protocols which
  support receiving Transfer-Encoding:chunked.

CVSS Score of 9.3


Updated Packages:

#This bug is fixed by Squid version 6.4.

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

Squid 5:

Squid 6:

  If you are using a prepackaged version of Squid then please refer
  to the package vendor for availability information on updated


Determining if your version is vulnerable:

  Squid older than 5.1 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 6.3 are vulnerable.



  * ICAP issues can be reduced by ensuring only trusted ICAP
    services are used, with TLS encrypted connections
    (ICAPS extension).

  *  There is no workaround for the HTTP Request Smuggling issue.


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

  For reporting of non-security bugs in the latest STABLE release
  the squid bugzilla database should be used

  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.



  This vulnerability was discovered by Keran Mu and Jianjun Chen,
  from Tsinghua University and Zhongguancun Laboratory.

  Fixed by Amos Jeffries of Treehouse Networks Ltd.


Revision history:

  2023-09-01 04:34:00 UTC Initial Report
  2023-10-01 08:43:00 UTC Patch Available

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