Moderate: nss security update

Updated nss packages that fix a security issue are now available for Red
Hat Enterprise Linux 4 and 5.

The Red Hat Security Response Team has rated this update as having moderate
security impact. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available from the CVE link in
the References section.

Network Security Services (NSS) is a set of libraries designed to support
the cross-platform development of security-enabled client and server
applications. Applications built with NSS can support SSLv2, SSLv3, TLS,
and other security standards.

Netscape Portable Runtime (NSPR) provides platform independence for non-GUI
operating system facilities. These facilities include threads, thread
synchronization, normal file and network I/O, interval timing, calendar
time, basic memory management (malloc and free), and shared library
linking.

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
this flaw: http://kbase.redhat.com/faq/docs/DOC-20491

Users of Red Hat Certificate System 7.3 and 8.0 should review the following
Knowledgebase article before installing this update:
http://kbase.redhat.com/faq/docs/DOC-28439

All users of NSS are advised to upgrade to these updated packages, which
update NSS to version 3.12.6. This erratum also updates the NSPR packages
to the version required by NSS 3.12.6. All running applications using the
NSS library must be restarted for this update to take effect.

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

533125 - CVE-2009-3555 TLS: MITM attacks via session renegotiation

https://www.redhat.com/security/data/cve/CVE-2009-3555.html
http://www.redhat.com/security/updates/classification/#moderate
http://kbase.redhat.com/faq/docs/DOC-20491
http://kbase.redhat.com/faq/docs/DOC-28439