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Vigil@nce - glibc: denial of service via swscanf
February 2015 by Vigil@nce
This bulletin was written by Vigil@nce : http://vigilance.fr/offer
SYNTHESIS OF THE VULNERABILITY
An attacker can consume too many memory in the swscanf() function
of the glibc, in order to trigger a denial of service.
Impacted products: Unix (platform)
Severity: 1/4
Creation date: 04/02/2015
DESCRIPTION OF THE VULNERABILITY
The swscanf() function of the glibc searches for a pattern in a
wide-character string.
Before reserving a stack memory area via alloca(), the swscanf()
function calls __libc_use_alloca() which checks if the requested
size is inferior to the limit __MAX_ALLOCA_CUTOFF. However, a
number of characters is compared instead of a number of bytes. The
alloca() function can thus be used up to 4 times the expected
limit, which may stop the application.
An attacker can therefore consume too many memory in the swscanf()
function of the glibc, in order to trigger a denial of service.
ACCESS TO THE COMPLETE VIGIL@NCE BULLETIN
http://vigilance.fr/vulnerability/glibc-denial-of-service-via-swscanf-16106
