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vulnerability alert CVE-2009-5138

GnuTLS: accepting X.509 CA v1

Synthesis of the vulnerability

An attacker can ask a trusted certification authority to create an X.509 v1 certificate, which is accepted by GnuTLS as being a root certificate.
Impacted products: RHEL, SUSE Linux Enterprise Desktop, SLES, Unix (platform) ~ not comprehensive.
Severity: 1/4.
Creation date: 26/02/2014.
Identifiers: 1069301, BID-65792, CVE-2009-5138, RHSA-2014:0247-01, SUSE-SU-2014:0319-1, SUSE-SU-2014:0320-1, SUSE-SU-2014:0322-1, SUSE-SU-2014:0445-1, VIGILANCE-VUL-14311.

Description of the vulnerability

An X.509 version 1 certificate does not have the basicConstraints extension. This extension indicates if the certificate if for a certification authority, and the number of allowed intermediary certifications authorities. For example:
   basicConstraints=critical, CA:TRUE, pathlen:0

However, by default, GnuTLS inferior to 2.7.6 allows v1 certificates.

An attacker can therefore ask a trusted certification authority to create an X.509 v1 certificate, which is accepted by GnuTLS as being a root certificate.
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