[squid-announce] [ADVISORY] SQUID-2024:2 Denial of Service in HTTP Header parser

[Amos Jeffries]

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     Squid Proxy Cache Security Update Advisory SQUID-2024:2
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Advisory ID:       | SQUID-2024:2
Date:              | Feb 15, 2024
Summary:           | Denial of Service in HTTP Header parser
Affected versions: | Squid 3.x -> 3.5.28
                    | Squid 4.x -> 4.17
                    | Squid 5.x -> 5.9
                    | Squid 6.x -> 6.4
Fixed in version:  | Squid 6.5
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Problem Description:

  Due to a Collapse of Data into Unsafe Value bug,
  Squid may be vulnerable to a Denial of Service
  attack against HTTP header parsing.

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Severity:

  This problem allows a remote client or a remote server to
  perform Denial of Service when sending oversized headers in
  HTTP messages.

  In versions of Squid prior to 6.5 this can be achieved if the
  request_header_max_size or reply_header_max_size settings are
  unchanged from the default.

  In Squid version 6.5 and later, the default setting of these
  parameters is safe. Squid will emit a critical warning in
  cache.log if the administrator is setting these parameters to
  unsafe values. Squid will not at this time prevent these settings
  from being changed to unsafe values.

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Updated Packages:

Hardening against this issue is added to Squid version 6.5.

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

Squid 6:
  <http://www.squid-cache.org/Versions/v6/SQUID-2024_2.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:

  Run the following command to identify how (and whether)
  your Squid has been configured with relevant settings:

     squid -k parse 2>&1 | grep header_max_size

  All Squid-3.0 up to and including 6.4 without header_max_size
  settings are vulnerable.

  All Squid-3.0 up to and including 6.4 with either header_max_size
  setting over 21 KB are vulnerable.

  All Squid-3.0 up to and including 6.4 with both header_max_size
  settings below 21 KB are not vulnerable.

  All Squid-6.5 and later without header_max_size configured
  are not vulnerable.

  All Squid-6.5 and later configured with both header_max_size
  settings below 64 KB are not vulnerable.

  All Squid-6.5 and later configured with either header_max_size
  setting over 64 KB are vulnerable.

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Workaround:

For Squid older than 6.5, add to squid.conf:

   request_header_max_size 21 KB
   reply_header_max_size 21 KB


For Squid 6.5 and later, remove request_header_max_size
  and reply_header_max_size from squid.conf

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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
  <https://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 by Joshua Rogers of Opera
  Software.

  Fixed by The Measurement Factory.

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Revision history:

  2023-10-12 11:53:02 UTC Initial Report
  2023-10-25 11:47:19 UTC Patches Released
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