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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2012.0012 Hash table implementations vulnerable to algorithmic complexity attacks 3 January 2012 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Apache Tomcat Microsoft .NET Framework Ruby PHP 5 Publisher: US-CERT Operating System: UNIX variants (UNIX, Linux, OSX) Windows Impact/Access: Denial of Service -- Remote/Unauthenticated Resolution: Patch/Upgrade CVE Names: CVE-2011-4885 CVE-2011-4838 CVE-2011-4815 CVE-2011-3414 Original Bulletin: http://www.kb.cert.org/vuls/id/903934 Comment: A hash collision denial of service condition has been found in multiple web programming languages. Some vendors have provided updates and/or workarounds; this bulletin provides additional information and workarounds. - --------------------------BEGIN INCLUDED TEXT-------------------- Vulnerability Note VU#903934 Hash table implementations vulnerable to algorithmic complexity attacks Overview Some programming language implementations do not sufficiently randomize their hash functions or provide means to limit key collision attacks, which can be leveraged by an unauthenticated attacker to cause a denial-of-service (DoS) condition. I. Description Many applications, including common web framework implementations, use hash tables to map key values to associated entries. If the hash table contains entries for different keys that map to the same hash value, a hash collision occurs and additional processing is required to determine which entry is appropriate for the key. If an attacker can generate many requests containing colliding key values, an application performing the hash table lookup may enter a denial of service condition. Hash collision denial-of-service attacks were first detailed in 2003, but recent research details how these attacks apply to modern language hash table implementations. II. Impact An application can be forced into a denial-of-service condition. In the case of some web application servers, specially-crafted POST form data may result in a denial-of-service. III. Solution Apply an update Please review the Vendor Information section of this document for vendor- specific patch and workaround details. Limit CPU time Limiting the processing time for a single request can help minimize the impact of malicious requests. Limit maximum POST size Limiting the maximum POST request size can reduce the number of possible predictable collisions, thus reducing the impact of an attack. Limit maximum request parameters Some servers offer the option to limit the number of parameters per request, which can also minimize impact. Vendor Information Vendor Status Date Notified Date Updated Adobe Unknown 2011-11-01 2011-11-01 http://www.kb.cert.org/vuls/id/MAPG-8N7Q7A Apache Tomcat Affected 2011-12-28 http://www.kb.cert.org/vuls/id/DWAN-8PYMUS IBM Corporation Unknown 2011-11-01 2011-11-01 http://www.kb.cert.org/vuls/id/MAPG-8N7Q7D Microsoft Corporation Affected 2011-11-01 2011-12-29 http://www.kb.cert.org/vuls/id/MAPG-8N7Q7G Oracle Corporation Unknown 2011-11-01 2011-11-01 http://www.kb.cert.org/vuls/id/MAPG-8N7Q7K Ruby Affected 2011-11-01 2011-12-28 http://www.kb.cert.org/vuls/id/MAPG-8N7Q7N The PHP Group Affected 2011-12-28 http://www.kb.cert.org/vuls/id/DWAN-8PYMFT References http://www.ocert.org/advisories/ocert-2011-003.html http://www.nruns.com/_downloads/advisory28122011.pdf http://www.cs.rice.edu/~scrosby/hash/CrosbyWallach_UsenixSec2003.pdf http://technet.microsoft.com/en-us/security/bulletin/ms11-100.mspx Credit Thanks to Alexander Klink and Julian Wlde for reporting these vulnerabilities. This document was written by Jared Allar and David Warren. Other Information Date Public: 2011-12-28 Date First Published: 2011-12-28 Date Last Updated: 2011-12-30 CERT Advisory: CVE-ID(s): CVE-2011-4815 CVE-2011-3414 CVE-2011-4838 CVE-2011-4885 NVD-ID(s): CVE-2011-4815 CVE-2011-3414 CVE-2011-4838 CVE-2011-4885 US-CERT Technical Alerts: Severity Metric: 10.80 Document Revision: 34 If you have feedback, comments, or additional information about this vulnerability, please send us email. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. 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If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQIVAwUBTwKQge4yVqjM2NGpAQLakg/+JiZjqXmvIagFeW1pkLc5eiKzHPDYvofj Pt+b6KjmP0BOTBHM75eL5/PrtPVKydIhbCOB5VqR0a9pGbFgY7UsTI7uRJkezELQ IjEasaY+UDwHiMeaEpVhsTgvsZtwBsS8Ga+hc2GKcjUOHxsv3SpOfpIgWVxE/CRF e1uuqNqbk1VSbY6vf2TRKx8yoiXgPUMoySl6WmuLqTebbIsmmEpGU//TwKjvH3dD 9Rz3yPH8XIxBG3fGZCiQWlczSwOzStL+0syb5ycSd/OARfbzsV+TJmYd197LKIjx UJhB8qU0zDPmJ2d1Jv7b7xrTb9Zo9Dyp808SpHiNo/Z2s1GMBpALvDCtu/WcVNwQ OLlxjJmHyr5HKZEzkeE2dGEuLoeoe5W2rendc5LfCJ61odyir0Je2hEotJunxFfv taBZJY7NlR9CBtqmO627VgZQTXsJGMPkYgzAJrY4my0iv9XDgEOBg1bC4d6ELr8k GCFBDtsTocuT9qUuzvdE4P7UB/iHJiXdEDvoSoRYu3wllcnNxbA/+Or7Fepdzpuh ghsaVbVqFpxLth5fLGVTyYTgt0GMDUV+CeVmMqxtTI94/6UNaFc5ACaLhoRvZLL4 I5WiafZetlCmGA55akobyRnA0p6/xlSP7eQdVmBsK1s2t20FdCmYA0B56OiwBvcR cO5o8tFrMXM= =FgeX -----END PGP SIGNATURE-----