Moderate: gnutls security update
Security Advisory: Moderate
Updated gnutls packages that fix two security issues are now available for
Red Hat Enterprise Linux 5.
The Red Hat Security Response Team has rated this update as having moderate
security impact. Common Vulnerability Scoring System (CVSS) base scores,
which give detailed severity ratings, are available for each vulnerability
from the CVE links in the References section.
The GnuTLS library provides support for cryptographic algorithms and for
protocols such as Transport Layer Security (TLS).
A flaw was found in the way the TLS/SSL (Transport Layer Security/Secure
Sockets Layer) protocols handled session renegotiation. A man-in-the-middle
attacker could use this flaw to prefix arbitrary plain text to a client's
session (for example, an HTTPS connection to a website). This could force
the server to process an attacker's request as if authenticated using the
victim's credentials. This update addresses this flaw by implementing the
TLS Renegotiation Indication Extension, as defined in RFC 5746.
(CVE-2009-3555)
Refer to the following Knowledgebase article for additional details about
the CVE-2009-3555 flaw: http://kbase.redhat.com/faq/docs/DOC-20491
Dan Kaminsky found that browsers could accept certificates with MD2 hash
signatures, even though MD2 is no longer considered a cryptographically
strong algorithm. This could make it easier for an attacker to create a
malicious certificate that would be treated as trusted by a browser. GnuTLS
now disables the use of the MD2 algorithm inside signatures by default.
(CVE-2009-2409)
Users of GnuTLS are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. For the update to take
effect, all applications linked to the GnuTLS library must be restarted, or
the system rebooted.
Before applying this update, make sure all previously-released errata
relevant to your system have been applied.
This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259
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