Freely subscribe to our NEWSLETTER

This bulletin was written by Vigil@nce : http://vigilance.fr/offer

SYNTHESIS OF THE VULNERABILITY

An attacker can force an error in the crypt() function, in order
to stop xlockmore, so a local attacker can access to X.

Impacted products: Fedora, Unix (platform)

Severity: 2/4

Creation date: 17/07/2013

DESCRIPTION OF THE VULNERABILITY

The xlockmore program locks the screen of an X session.

The crypt() function of the glibc hashes a password, using a salt
(random). Since glibc version 2.17, the crypt() function returns a
NULL pointer if the salt is malformed. However, xlockmore does not
handle this case, and dereferences a NULL pointer. The process is
then stopped.

An attacker can therefore force an error in the crypt() function,
in order to stop xlockmore, so a local attacker can access to X.

ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN

http://vigilance.fr/vulnerability/xlockmore-denial-of-service-via-crypt-13135