Actu
Vigil@nce: GnuTLS, incorrect certificate chain verification
November 2008 by Vigil@nce
SYNTHESIS
An attacker can use an invalid certification chain which is not
rejected by GnuTLS, in order to create a man-in-the-middle attack.
Gravity: 2/4
Consequences: data reading, data flow
Provenance: internet server
Means of attack: 1 attack
Ability of attacker: technician (2/4)
Confidence: confirmed by the editor (5/5)
Diffusion of the vulnerable configuration: high (3/3)
Creation date: 17/11/2008
IMPACTED PRODUCTS
– Mandriva Linux
– Slackware Linux
– Unix - plateform
DESCRIPTION
The GnuTLS library can be used to implement TLS/SSL
clients/servers.
The VIGILANCE-VUL-8235 (https://vigilance.fr/tree/1/8235)
vulnerability can be used by an attacker to create an invalid
certification chain which is accepted by GnuTLS. This
vulnerability was corrected in version 2.6.1 (VIGILANCE-SOL-16440
(https://vigilance.fr/tree/2/16440).
However, version 2.6.1 creates a new vulnerability. Indeed, when
the certificate chain contains only one self-signed certificates,
it is accepted as valid.
An attacker can for example setup a malicious web site offering
this certification chain, in order to deceive web clients linked
to GnuTLS.
CHARACTERISTICS
Identifiers: 505279, MDVSA-2008:227-1, SSA:2008-320-01,
VIGILANCE-VUL-8249
Pointed by: VIGILANCE-SOL-16440
