[arch-security] [ASA-201609-25] gnutls: certificate verification bypass

[Levente Polyak]

Arch Linux Security Advisory ASA-201609-25
==========================================

Severity: Medium
Date    : 2016-09-26
CVE-ID  : CVE-2016-7444
Package : gnutls
Type    : certificate verification bypass
Remote  : Yes
Link    : https://wiki.archlinux.org/index.php/CVE

Summary
=======

The package gnutls before version 3.4.15-1 is vulnerable to certificate
verification bypass.

Resolution
==========

Upgrade to 3.4.15-1.

# pacman -Syu "gnutls>=3.4.15-1"

The problem has been fixed upstream in version 3.4.15.

Workaround
==========

None.

Description
===========

Incorrect length validation on gnutls's gnutls_ocsp_resp_check_crt
method can allow an attacker to use a OCSP response for a different
certificate (but from the same CA) to continue using a revoked
certificate. This can happen if the serial from the revoked certificate
is a prefix of the other one, and the additional bytes happen to be
equal on the system doing the verification.

Impact
======

A remote attacker is able to bypass certificate verification and
continue using a revoked certificate under certain circumstances.

References
==========

https://lists.gnupg.org/pipermail/gnutls-devel/2016-September/008146.html
https://gitlab.com/gnutls/gnutls/commit/964632f37dfdfb914ebc5e49db4fa29af35b1de9
https://access.redhat.com/security/cve/CVE-2016-7444

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