RHSA-2010:0166: Moderate: gnutls security update

First published: Thu Mar 25 2010(Updated: )

The GnuTLS library provides support for cryptographic algorithms and for<br>protocols such as Transport Layer Security (TLS).<br>A flaw was found in the way the TLS/SSL (Transport Layer Security/Secure<br>Sockets Layer) protocols handled session renegotiation. A man-in-the-middle<br>attacker could use this flaw to prefix arbitrary plain text to a client's<br>session (for example, an HTTPS connection to a website). This could force<br>the server to process an attacker's request as if authenticated using the<br>victim's credentials. This update addresses this flaw by implementing the<br>TLS Renegotiation Indication Extension, as defined in RFC 5746.<br>(CVE-2009-3555)<br>Refer to the following Knowledgebase article for additional details about<br>the CVE-2009-3555 flaw: <a href="http://kbase.redhat.com/faq/docs/DOC-20491" target="_blank">http://kbase.redhat.com/faq/docs/DOC-20491</a> Dan Kaminsky found that browsers could accept certificates with MD2 hash<br>signatures, even though MD2 is no longer considered a cryptographically<br>strong algorithm. This could make it easier for an attacker to create a<br>malicious certificate that would be treated as trusted by a browser. GnuTLS<br>now disables the use of the MD2 algorithm inside signatures by default.<br>(CVE-2009-2409)<br>Users of GnuTLS are advised to upgrade to these updated packages, which<br>contain backported patches to correct these issues. For the update to take<br>effect, all applications linked to the GnuTLS library must be restarted, or<br>the system rebooted.

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