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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2009.0157 -- [FreeBSD] telnetd code execution vulnerability 23 February 2009 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: telnetd Publisher: FreeBSD Operating System: FreeBSD Impact: Root Compromise Access: Remote/Unauthenticated CVE Names: CVE-2009-0641 Original Bulletin: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-09:05.telnetd.asc Revision History: February 23 2009: Added CVE Reference February 17 2009: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-09:05.telnetd Security Advisory The FreeBSD Project Topic: telnetd code execution vulnerability Category: core Module: contrib Announced: 2009-02-16 Affects: FreeBSD 7.x Corrected: 2009-02-16 21:56:17 UTC (RELENG_7, 7.1-STABLE) 2009-02-16 21:56:17 UTC (RELENG_7_1, 7.1-RELEASE-p10) 2009-02-16 21:56:17 UTC (RELENG_7_0, 7.0-RELEASE-p3) For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:http://security.FreeBSD.org/>. I. Background The FreeBSD telnet daemon, telnetd(8), implements the server side of the TELNET virtual terminal protocol. It has been disabled by default in FreeBSD since August 2001, and due to the lack of cryptographic security in the TELNET protocol, it is strongly recommended that the SSH protocol be used instead. The FreeBSD telnet daemon can be enabled via the /etc/inetd.conf configuration file and the inetd(8) daemon. The TELNET protocol allows a connecting client to specify environment variables which should be set in any created login session; this is used, for example, to specify terminal settings. II. Problem Description In order to prevent environment variable based attacks, telnetd(8) "scrubs" its environment; however, recent changes in FreeBSD's environment-handling code rendered telnetd's scrubbing inoperative, thereby allowing potentially harmful environment variables to be set. III. Impact An attacker who can place a specially-constructed file onto a target system (either by legitimately logging into the system or by exploiting some other service on the system) can execute arbitrary code with the privileges of the user running the telnet daemon (usually root). IV. Workaround No workaround is available, but systems which are not running the telnet daemon are not vulnerable. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_1 or RELENG_7_0 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 7.0 and 7.1 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch # fetch http://security.FreeBSD.org/patches/SA-09:05/telnetd.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch # cd /usr/src/lib/libtelnet # make obj && make depend && make # cd /usr/src/libexec/telnetd # make obj && make depend && make && make install VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. CVS: Branch Revision Path - - ------------------------------------------------------------------------- RELENG_7 src/contrib/telnet/telnetd/sys_term.c 1.18.22.1 RELENG_7_1 src/UPDATING 1.507.2.13.2.6 src/sys/conf/newvers.sh 1.72.2.9.2.7 src/contrib/telnet/telnetd/sys_term.c 1.18.30.2 RELENG_7_0 src/UPDATING 1.507.2.3.2.14 src/sys/conf/newvers.sh 1.72.2.5.2.14 src/contrib/telnet/telnetd/sys_term.c 1.18.26.1 - - ------------------------------------------------------------------------- Subversion: Branch/path Revision - - ------------------------------------------------------------------------- stable/7/ r188699 releng/7.1/ r188699 releng/7.0/ r188699 - - ------------------------------------------------------------------------- VII. References http://lists.grok.org.uk/pipermail/full-disclosure/2009-February/067954.html The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-09:05.telnetd.asc - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkmZ4dwACgkQFdaIBMps37JI2gCfZsCqw/ev/qVKELwNiFxj8zra aooAn0GU4wBW7jBulFhrSyXtKVlgs18B =joA6 - -----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. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. 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 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 iD8DBQFJoe0TNVH5XJJInbgRAjsOAJ4k0/RiFAuaLNnlA5/aRKyM67A69ACfbF4i /6+LBILiPbEIKx5qH5CfesE= =kCjc -----END PGP SIGNATURE-----