J-Security Center

Title: gnuserv MIT-MAGIC-COOKIE Remote Buffer Overflow Vulnerability

Severity: MODERATE

Description:

gnuserv is a freely available client server package included with xemacs. gnuserv is currently maintained by Jan Vroonhof.

A problem with gnuserv could allow a remote user to arbitrarily execute code. gnuserv allows for remote connectivity to a local session using the MIT-MAGIC-COOKIE authentication mechanism. However, the server places trust in the remote side of the connection to send a magic cookie within the size limitations. Sanity checks are not done on the cookie, which could allow a buffer overflow in the buffer holding the cookie, or alter the prefix length of authentication to a new size of 1 byte, making it possible to launch a brute-force attack against a trivial authentication.

This makes it possible for a remote user to initiate a connection to the gnuserv server, and potentially execute code as the UID of the server.

Affected Products:

  • MandrakeSoft Corporate Server 1.0.1
  • MandrakeSoft Linux Mandrake 6.0.0
  • MandrakeSoft Linux Mandrake 6.1.0
  • MandrakeSoft Linux Mandrake 7.0.0
  • MandrakeSoft Linux Mandrake 7.1.0
  • MandrakeSoft Linux Mandrake 7.2.0
  • Martin Schwenkes gnuserv 3.11.0
  • RedHat Linux 6.2.0 alpha
  • RedHat Linux 6.2.0 i386
  • RedHat Linux 6.2.0 sparc
  • XEmacs Development Team XEmacs 2.1.13
  • XEmacs Development Team XEmacs 21.2.42

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