CVE-2015-6251: Use After Free

Published Aug 10, 2015
·
Updated

A use-after-free flaw was found in GnuTLS's gnutlsx509dntostring() function. A remote attacker could create a specially crafted certificate with very long DistinguishedName (DN) entries that, when processed by an application compiled against GnuTLS, could cause that application to crash.

This issue was fixed in upstream versions 3.4.4 and 3.3.17 of GnuTLS:

https://lists.gnupg.org/pipermail/gnutls-devel/2015-August/007707.html https://lists.gnupg.org/pipermail/gnutls-devel/2015-August/007708.html

The following patch fixes this issue:

https://gitlab.com/gnutls/gnutls/commit/272854367efc130fbd4f1a51840d80c630214e12

The affected function, gnutlsx509dntostring(), was first introduced in version 3.1.10 via commit:

https://gitlab.com/gnutls/gnutls/commit/6be35136333b5d6289f23209cf896e741462909a

The gnutls packages in Red Hat Enterprise Linux 6 and earlier include GnuTLS versions 2.x or 1.x and are therefore not affected by this issue.

External References:

http://www.gnutls.org/security.html#GNUTLS-SA-2015-3

Other sources

Double free vulnerability in GnuTLS before 3.3.17 and 3.4.x before 3.4.4 allows remote attackers to cause a denial of service via a long DistinguishedName (DN) entry in a certificate.

— MITRE

Affected Software

25 affected componentsFixes available
redhat/gnutls<3.4.4
3.4.4
redhat/gnutls<3.3.17
3.3.17
GNU GnuTLS=3.3.0
GNU GnuTLS=3.3.0-pre0
GNU GnuTLS=3.3.1
GNU GnuTLS=3.3.2
GNU GnuTLS=3.3.3
GNU GnuTLS=3.3.4
GNU GnuTLS=3.3.5
GNU GnuTLS=3.3.6
GNU GnuTLS=3.3.7
GNU GnuTLS=3.3.8
GNU GnuTLS=3.3.9
GNU GnuTLS=3.3.10
GNU GnuTLS=3.3.11
GNU GnuTLS=3.3.12
GNU GnuTLS=3.3.13
GNU GnuTLS=3.3.14
GNU GnuTLS=3.3.15
GNU GnuTLS=3.3.16
GNU GnuTLS=3.4.0
GNU GnuTLS=3.4.1
GNU GnuTLS=3.4.2
GNU GnuTLS=3.4.3
Debian Debian Linux=8.0

Event History

Aug 24, 2015
CVE Published
via MITRE·02:00 PM
Data Sourced
via MITRE·02:00 PM
Description
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Frequently Asked Questions

1

What is the severity of CVE-2015-6251?

CVE-2015-6251 has a medium severity rating, as it can lead to a denial of service by crashing the application.

2

How do I fix CVE-2015-6251?

To fix CVE-2015-6251, upgrade GnuTLS to version 3.4.4 or later, or version 3.3.17 or later.

3

Which versions of GnuTLS are affected by CVE-2015-6251?

CVE-2015-6251 affects GnuTLS versions prior to 3.4.4 and 3.3.17.

4

What can an attacker do with CVE-2015-6251?

An attacker can exploit CVE-2015-6251 by sending a specially crafted certificate to an application using GnuTLS, causing it to crash.

5

How can I determine if my application is vulnerable to CVE-2015-6251?

Check the version of GnuTLS linked to your application; if it's older than 3.4.4 or 3.3.17, it is vulnerable to CVE-2015-6251.

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