Published:
06 September 2004
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2004.0556 -- US-CERT Technical Cyber Security Alert TA04-247A Vulnerabilities in MIT Kerberos 5 6 September 2004 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: MIT Kerberos 5 versions prior to krb5-1.3.5 Applications that use MIT Kerberos 5 libraries Applications with code derived from MIT Kerberos 5 Publisher: US-CERT Impact: Root Compromise Execute Arbitrary Code/Commands Denial of Service Access: Remote/Unauthenticated CVE Names: CAN-2004-0642 CAN-2004-0643 CAN-2004-0644 CAN-2004-0772 Ref: AL-2004.026 ESB-2004.0551 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 National Cyber Alert System Technical Cyber Security Alert TA04-247A Vulnerabilities in MIT Kerberos 5 Original release date: September 3, 2004 Last revised: -- Source: US-CERT Systems Affected * MIT Kerberos 5 versions prior to krb5-1.3.5 * Applications that use versions of MIT Kerberos 5 libraries prior to krb5-1.3.5 * Applications that contain code derived from MIT Kerberos 5 Updated vendor information is available in the systems affected section of the individual vulnerability notes. Overview The MIT Kerberos 5 implementation contains several vulnerabilities, the most severe of which could allow an unauthenticated, remote attacker to execute arbitrary code on a Kerberos Distribution Center (KDC). This could result in the compromise of an entire Kerberos realm. I. Description There are several vulnerabilities in the MIT implementation of the Kerberos 5 protocol. With one exception (VU#550464), all of the vulnerabilities involve insecure deallocation of heap memory (double-free vulnerabilities) during error handling and Abstract Syntax Notation One (ASN.1) decoding. For further details, please see the following vulnerability notes: VU#795632 - MIT Kerberos 5 ASN.1 decoding functions insecurely deallocate memory (double-free) The MIT Kerberos 5 library does not securely deallocate heap memory when decoding ASN.1 structures, resulting in double-free vulnerabilities. An unauthenticated, remote attacker could execute arbitrary code on a KDC server, which could compromise an entire Kerberos realm. An attacker may also be able to execute arbitrary code on Kerberos clients, or cause a denial of service on KDCs or clients. (Other resources: MITKRB5-SA-2004-002, CAN-2004-0642) VU#866472 - MIT Kerberos 5 ASN.1 decoding function krb5_rd_cred() insecurely deallocates memory (double-free) The krb5_rd_cred() function in the MIT Kerberos 5 library does not securely deallocate heap memory when decoding ASN.1 structures, resulting in a double-free vulnerability. A remote, authenticated attacker could execute arbitrary code or cause a denial of service on any system running an application that calls krb5_rd_cred(). This includes Kerberos application servers and other applications that process Kerberos authentication via the MIT Kerberos 5 library, Generic Security Services Application Programming Interface (GSSAPI), and other libraries. (Other resources: MITKRB5-SA-2004-002, CAN-2004-0643) VU#350792 - MIT Kerberos krb524d insecurely deallocates memory (double-free) The MIT Kerberos krb524d daemon does not securely deallocate heap memory when handling an error condition, resulting in a double-free vulnerability. An unauthenticated, remote attacker could execute arbitrary code on a system running krb524d, which in many cases is also a KDC. The compromise of a KDC system can lead to the compromise of an entire Kerberos realm. An attacker may also be able to cause a denial of service on a system running krb524d. (Other resources: MITKRB5-SA-2004-002, CAN-2004-0772) VU#550464 - MIT Kerberos 5 ASN.1 decoding function asn1buf_skiptail() does not properly terminate loop The asn1buf_skiptail() function in the MIT Kerberos 5 library does not properly terminate a loop, allowing an unauthenticated, remote attacker to cause a denial of service in a KDC, application server, or Kerberos client. (Other resources: MITKRB5-SA-2004-003, CAN-2004-0644) II. Impact The impacts of these vulnerabilities vary, but an attacker may be able to execute arbitrary code on KDCs, systems running krb524d (typically also KDCs), application servers, applications that use Kerberos libraries directly or via GSSAPI, and Kerberos clients. An attacker could also cause a denial of service on any of these systems. The most severe vulnerabilities could allow an unauthenticated, remote attacker to execute arbitrary code on a KDC system. This could result in the compromise of both the KDC and an entire Kerberos realm. III. Solution Apply a patch or upgrade Check with your vendor(s) for patches or updates. For information about a specific vendor, please see the systems affected sections in the individual vulnerability notes or contact your vendor directly. Alternatively, apply the appropriate source code patch(es) referenced in MITKRB5-SA-2004-002 and MITKRB5-SA-2004-003 and recompile. These vulnerabilities will be addressed in krb5-1.3.5. Appendix A. References * Vulnerability Note VU#795632 - <http://www.kb.cert.org/vuls/id/795632> * Vulnerability Note VU#866472 - <http://www.kb.cert.org/vuls/id/866472> * Vulnerability Note VU#350792 - <http://www.kb.cert.org/vuls/id/350792> * Vulnerability Note VU#550464 - <http://www.kb.cert.org/vuls/id/550464> * MIT krb5 Security Advisory 2004-002 - <http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2004-002-dblfre e.txt> * MIT krb5 Security Advisory 2004-003 - <http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2004-003-as n1.txt> * Kerberos: The Network Authentication Protocol - <http://web.mit.edu/kerberos/www/> _______________________________________________________________________ Thanks to Tom Yu and the MIT Kerberos Development team for addressing these vulnerabilities and coordinating with vendors. MIT credits the following people: Will Fiveash, Joseph Galbraith, John Hawkinson, Marc Horowitz, and Nico Williams. _______________________________________________________________________ Feedback can be directed to the author: Art Manion _______________________________________________________________________ This document is available from: <http://www.us-cert.gov/cas/techalerts/TA04-245A.html> _______________________________________________________________________ Copyright 2004 Carnegie Mellon University. Terms of use Terms of use: <http://www.us-cert.gov/legal.html> _______________________________________________________________________ Revision History September 3, 2004: Initial release - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) iD8DBQFBOM3iXlvNRxAkFWARAs9xAKC23q9EekPz/InQVWZPeUVhH4bnKwCgkVfh vKAOqE4sCXyydZ4BKnNreK8= =7R1M - -----END PGP SIGNATURE----- - --------------------------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. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== 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 iQCVAwUBQTwR/Sh9+71yA2DNAQJPGgQAgWfhkNlOQUwUnUMzOefngNs2r6R+hEDg gp35RAr+Vkakiorf7qCbsGONPGty32pzyTSUlIsFBc9FCaEUUOw6mA3ppQfEhAA6 YxlITCPH6oUFmIYgCNuosjZZvgKG482u9ZwSbgGdg7NwQi6u3WUl9PsUBEpIcBov jqCj/6lpJl4= =g79b -----END PGP SIGNATURE-----