From security-advisories@freebsd.org Mon Jul 15 20:08:34 2002 From: FreeBSD Security Advisories To: Bugtraq Date: Mon, 15 Jul 2002 10:01:55 -0700 (PDT) Subject: FreeBSD Security Advisory FreeBSD-SA-02:31.openssh -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-02:31 Security Advisory The FreeBSD Project Topic: openssh contains remote vulnerability Category: core Module: OpenSSH Announced: 2002-07-15 Credits: ISS X-Force Theo DeRaadt Affects: FreeBSD-CURRENT between 2002-03-18 and 2002-06-25 Corrected: 2002-06-25 19:10:07 (HEAD) FreeBSD only: NO I. Background OpenSSH is a free implementation of the SSH protocol suite, and provides encrypted and authenticated remote login, file transfer and command execution. II. Problem Description SSH clients and servers communicate by exchanging discrete messages with a variable number of parameters. Due to the lack of sufficient integrity checks in a portion of the server code responsible for handling incoming SSH2_MSG_USERAUTH_INFO_RESPONSE messages, it was possible for a malicious client to send a message that would cause the server to overwrite portions of its memory with client-provided data. III. Impact An remote attacker using an SSH client modified to send carefully crafted SSH2_MSG_USERAUTH_INFO_RESPONSE to the server could obtain superuser privileges on the server. Please note that this problem only affects FreeBSD-CURRENT. No versions of FreeBSD-STABLE are or were ever vulnerable to this bug. IV. Workaround Do one of the following: 1) Disable SSH entirely. 2) Use a firewall to block incoming SSH connections from untrusted hosts. 3) Add the following line to /etc/ssh/sshd_config, and restart sshd. ChallengeResponseAuthentication no Note that this will prevent the use of OPIE and similar challenge- based authentication methods with SSH. V. Solution Update your system to the latest -CURRENT. VI. Correction details No correction details are provided in this advisory. VII. References -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (FreeBSD) Comment: FreeBSD: The Power To Serve iQCVAwUBPTLiBVUuHi5z0oilAQFNAwQAoF1azTbsIiUc9O2VvIah+ueT5N3//qgf ka+t5I5FtL8wFDKJXXf3JWx9lqf+JkscrL4SpMyY/OmL2wagvUeVHan+pE9dXRnK YzFjdD8hP3GMiC1g0Dvwg9StoBs8kx+qP8dascS87Ql2QYo7aYcq6aageLSoy4Nj iRHaJB2gZP8= =nSnf -----END PGP SIGNATURE-----