[squid-announce] [ADVISORY] SQUID-2020:5 Denial of Service when using SMP cache

[Amos Jeffries]

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    Squid Proxy Cache Security Update Advisory SQUID-2020:5
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 Advisory ID:       | SQUID-2020:5
 Date:              | June 19, 2020
 Summary:           | Denial of Service when using SMP cache
 Affected versions: | 5.0.1 -> 5.0.2
 Fixed in version:  | 5.0.3
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  <http://www.squid-cache.org/Advisories/SQUID-2020_5.txt>
  <http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-14059>

<https://github.com/squid-cache/squid/security/advisories/GHSA-w7pw-2m4p-58hr>
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Problem Description:

 Due to an Incorrect Synchronization, Squid is vulnerable to a
 Denial of Service attack when processing objects in an SMP cache.

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Severity:

 This problem may allow a remote client to trigger a Squid worker
 assertion.

 This attack is limited to SMP Squids using shared memory cache
 and/or an SMP rock disk cache.

 CVSS Score of 7.3
<https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C/CR:X/IR:X/AR:H/MAV:N/MAC:H/MPR:L/MUI:N/MS:C/MC:N/MI:X/MA:H&version=3.1>

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Updated Packages:

This bug is fixed in Squid version 5.0.3.

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

Squid 5:
 <http://www.squid-cache.org/Versions/v5/changesets/squid-5-7a5af8db8e0377c06ed9ffbdcb1334389c7cd8ab.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:

 All Squid-3.x up to and including 3.5.28 are not vulnerable.

 All Squid-4.x up to and including 4.12 are not vulnerable.

 Squid-5.0.1 and 5.0.2 not using SMP caching are not vulnerable.

 Squid-5.0.1 and 5.0.2 using SMP caching are vulnerable.

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Workarounds:

Disable all SMP caching. For example:

 * If using multiple Squid workers, set 'cache_mem' to '0' and
   remove all `cache_dir` directives from squid.conf.

 * If using a single Squid worker, remove all 'cache_dir rock'
   directives 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 your 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 by Jack Zar of Bloomberg.

 Fixed by Alex Rousskov of The Measurement Factory.

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Revision history:

 2020-03-02 16:45:44 UTC Initial Report
 2020-05-13 06:37:31 UTC Patch Released
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