-----BEGIN PGP SIGNED MESSAGE----- KRB5 TELNETD BUFFER OVERFLOWS 2001-07-31 SUMMARY: Buffer overflows exist in the telnet daemon included with MIT krb5. Exploits are believed to exist for various operating systems on at least the i386 architecture. IMPACT: If telnetd is running, a remote user may gain unauthorized root access. VULNERABLE DISTRIBUTIONS: * MIT Kerberos 5, all releases to date. FIXES: The recommended approach is to apply the appropriate patches and to rebuild your telnetd. Patches for the krb5-1.2.2 release may be found at: http://web.mit.edu/kerberos/www/advisories/telnetd_122_patch.txt The associated detached PGP signature is at: http://web.mit.edu/kerberos/www/advisories/telnetd_122_patch.txt.asc These patches might apply successfully to older releases with some amount of fuzz. Please note that if you are using GNU make to build your krb5 sources, the build system may attempt to rebuild the configure script from the changed configure.in. This may cause trouble if you don't have autoconf installed properly. To prevent this, you should use the touch command or some similar means to ensure that the file modification time on the configure script is newer than that of the configure.in file. If you are unable to patch your telnetd, you may should disable the telnet service altogether. This announcement and code patches related to it may be found on the MIT Kerberos security advisory page at: http://web.mit.edu/kerberos/www/advisories/index.html The main MIT Kerberos web page is at: http://web.mit.edu/kerberos/www/index.html ACKNOWLEDGMENTS: Thanks to TESO for the original alert / Bugtraq posting. Thanks to Jeffrey Altman for assistance in developing these patches. DETAILS: A buffer overflow bug was discovered in telnet daemons derived from BSD source code. Since the telnet daemon in MIT krb5 uses code largely derived originally from BSD sources, it too is vulnerable. By carefully constructing a series of telnet options to send to a telnet server, a remote attacker may exercise a bug relating to lack of bounds-checking, causing an overflow of a fixed-size buffer. This overflow may possibly force the execution of malicious code. It is not known how difficult this vulnerability is to exploit, since the buffer is not on the stack. Some discussion seems to indicate that exploits exist for this vulnerability that are believed to work against various operating systems for i386-based machines. It is not known whether these existing exploits have been successfully ported to other processors. -----BEGIN PGP SIGNATURE----- Version: PGP 6.5.8 iQCVAwUBO2cP4qbDgE/zdoE9AQEdhQQAsAxuzVwWu7pbtZ8ouNK7VAFrODGBHJ6R AxizbvpPMEUAPmHtNqyC+J7hmdcumAxm4ro1dQ6qqZrpV8e8X+MykNoOkt7jbzqz Q3KgfV8DkEthtoZ7M6asMrNScE6tBU6hfBAk33RU25vHMM42PRdRjliIDCCJl3pu /slqReyHFTg= =i6/X -----END PGP SIGNATURE-----
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