__________________________________________________________________ Squid Proxy Cache Security Update Advisory SQUID-2018:5 __________________________________________________________________ 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 __________________________________________________________________ http://www.squid-cache.org/Advisories/SQUID-2018_5.txt http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-19132 __________________________________________________________________ Problem Description: Due to a memory leak in SNMP query rejection code, Squid is vulnerable to a denial of service attack. __________________________________________________________________ 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. __________________________________________________________________ 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/SQUID-2018_5.patch If you are using a prepackaged version of Squid then please refer to the package vendor for availability information on updated packages. __________________________________________________________________ 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 __________________________________________________________________ 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. __________________________________________________________________ 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@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@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. __________________________________________________________________ Credits: This vulnerability was discovered and fixed by Florian Kohnhäuser __________________________________________________________________ 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 2018-11-09 12:45:01 UTC CVE Assignment __________________________________________________________________ END