[squid-users] [squid-announce] [ADVISORY] SQUID-2018:5 Denial of Service issue in SNMP processing

[Amos Jeffries]

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    Squid Proxy Cache Security Update Advisory SQUID-2018:5
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Advisory ID:        SQUID-2018:5
Date:               October 28, 2018
Summary:            Denial of Service issue
                    in SNMP processing.
Affected versions:  Squid 3.2.0.10 -> 3.5.28
                    Squid 4.x -> 4.3
Fixed in version:   Squid 4.4
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    http://www.squid-cache.org/Advisories/SQUID-2018_5.txt
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Problem Description:

 Due to a memory leak in SNMP query rejection code, Squid is
 vulnerable to a denial of service attack.

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Severity:

 This problem allows a remote attacker to consume all memory
 available to the Squid process, causing it to crash.

 In environments where per-process memory restrictions are not
 enforced strictly, or configured to large values this may also
 affect other processes operating on the same machine. Leading to
 a much worse denial of service situation.

 This problem is limited to Squid built with SNMP support and
 receiving SNMP traffic.

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Updated Packages:

 This bug is fixed by Squid version 4.4.

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

Squid 3.5:
 http://www.squid-cache.org/Versions/v3/3.5/changesets/squid-3.5-bc9786119f058a76ddf0625424bc33d36460b9a2.patch

Squid 4:
 http://www.squid-cache.org/Versions/v4/changesets/squid-4-983c5c36e5f109512ed1af38a329d0b5d0967498.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 built with --disable-snmp are not vulnerable.

 All Squid-2.x and older versions are not vulnerable.

 All Squid-3.x up to and including 3.2.0.9 are not vulnerable.

 All Squid-3.x up to and including 3.5.28 configured with
 "snmp_port 0" are not vulnerable.

 All Squid-3.x up to and including 3.5.28 without snmp_port
 configured are not vulnerable.

 All Squid-3.2.0.10 and later 3.2.x versions with snmp_port
 configured to a non-0 value are vulnerable.

 All Squid-3.3 versions up to and including 3.3.14 with snmp_port
 configured to a non-0 value are vulnerable.

 All Squid-3.4 versions up to and including 3.4.14 with snmp_port
 configured to a non-0 value are vulnerable.

 All Squid-3.5 versions up to and including 3.5.28 with snmp_port
 configured to a non-0 value are vulnerable.

 All Squid-4.x versions up to and including 4.3 with snmp_port
 configured to a non-0 value are vulnerable.


To determine the version of your Squid and its build options use
the command:

 squid -v

To determine whether snmp_port is configured use the command:

 squid -k parse | grep snmp_port

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Workarounds:

Either;

 Enable firewall inspection of SNMP packets to enforce blocking
 of any non-permitted packets prior to their arriving at Squid.

 This restriction of packet sources reduces the risk, but does not
 completely remove the vulnerability.

Or,

 Remove snmp_port and related configuration settings until Squid
 can be upgraded to a fixed build.

 This completely removes the vulnerability at cost of reduced
 management and monitoring capabilities.

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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 and fixed by Florian Kohnhäuser

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Revision history:

 2018-10-23 06:15:46 UTC Initial Report
 2018-10-23 21:42:58 UTC Patch Released
 2018-10-27 21:19:00 UTC Packages Released
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END
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