__________________________________________________________________ Squid Proxy Cache Security Update Advisory SQUID-2016:6 __________________________________________________________________ Advisory ID: SQUID-2016:6 Date: April 20, 2016 Summary: Multiple issues in ESI processing. Affected versions: Squid 3.x -> 3.5.16 Squid 4.x -> 4.0.8 Fixed in version: Squid 3.5.17, 4.0.9 __________________________________________________________________ http://www.squid-cache.org/Advisories/SQUID-2016_6.txt http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4052 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4053 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4054 CESG REF: 56284998 / VULNERABILITY ID: 393536 __________________________________________________________________ Problem Description: Due to buffer overflow issues Squid is vulnerable to a denial of service attack when processing ESI responses. Due to incorrect input validation Squid is vulnerable to public information disclosure of the server stack layout when processing ESI responses. Due to incorrect input validation and buffer overflow Squid is vulnerable to remote code execution when processing ESI responses. __________________________________________________________________ Severity: These problems allow ESI components to be used to perform a denial of service attack on the Squid service and all other services on the same machine. Under certain build conditions these problems allow remote clients to view large sections of the server memory. However, the bugs are exploitable only if you have built and configured the ESI features to be used by a reverse-proxy and if the ESI components being processed by Squid can be controlled by an attacker. __________________________________________________________________ Updated Packages: These bugs are fixed by Squid version 3.5.17 and 4.0.9. In addition, patches addressing this problem for stable releases can be found in our patch archives: Squid 3.2: Squid 3.3: Squid 3.4: Squid 3.5: 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: Use the command 'squid -v' to view version and build details of your proxy; All Squid 2.x are not vulnerable. All Squid built with --disable-esi are not vulnerable. All Squid built without --enable-esi are not vulnerable. Check squid.conf or use the (version 3.4+) command (squid -k parse 2>&1) | grep "Processing: http.*_port" to view the active configuration settings for your proxy; Unpatched Squid 3.x and 4.x built with --enable-esi and configured with 'accel' or 'vhost' or 'defaultsite=' or 'ssl-bump' on an http_port or https_port are vulnerable. All Squid configured without reverse-proxy or ssl-bump are not vulnerable. __________________________________________________________________ Workaround: Build Squid with --disable-esi if ESI is not needed. __________________________________________________________________ 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@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 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@squid-cache.org mailing list. It is a closed list (though anyone can post) and security related bug reports are treated in confidence until the impact has been established. __________________________________________________________________ Credits: The vulnerability was reported by CESG. Fixed by Amos Jeffries, Treehouse Networks Ltd. __________________________________________________________________ Revision history: 2016-04-15 10:54:39 GMT Initial Report 2016-04-20 03:54:54 GMT Patches Released 2016-04-20 13:42:00 GMT Packages Released 2016-04-20 15:47:01 GMT CVE Assigned __________________________________________________________________ END