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Debian Security Advisory DSA-2141-2                  security@debian.org
http://www.debian.org/security/                           Stefan Fritsch
January 06, 2011                      http://www.debian.org/security/faq
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Package        : nss
Vulnerability  : SSL/TLS insecure renegotiation protocol design flaw
Problem type   : remote
Debian-specific: no
CVE ID         : CVE-2009-3555

CVE-2009-3555:

Marsh Ray, Steve Dispensa, and Martin Rex discovered a flaw in the TLS
and SSLv3 protocols. If an attacker could perform a man in the middle
attack at the start of a TLS connection, the attacker could inject
arbitrary content at the beginning of the user's session. This update
adds backported support for the new RFC5746 renegotiation extension
which fixes this issue.

The updated libraries allow to use shell environment variables to
configure if insecure renegotiation is still allowed. The syntax of
these environment variables is described in the release notes to
version 3.12.6 of nss:
 

However, the default behaviour for nss in Debian 5.0 (Lenny) is 
NSS_SSL_ENABLE_RENEGOTIATION=3, which allows clients to continue to
renegotiate with vulnerable servers.

For the stable distribution (lenny), this problem has been fixed
in version 3.12.3.1-0lenny3.

For the unstable distribution (sid), and the testing distribution
(squeeze), this problem has been fixed in version 3.12.6-1.

We recommend that you upgrade your nss package.

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: http://www.debian.org/security/

Mailing list: debian-security-announce@lists.debian.org