Crypto Error Leaves Hundreds of Applications Open to Fake Certificates

Any site or application that uses GnuTLS to authenticate certificates is at risk for exploit
Any site or application that uses GnuTLS to authenticate certificates is at risk for exploit

GnuTLS provides support for cryptographic algorithms like SSL and for protocols such as Transport Layer Security (TLS). An open-source offering, it’s used by a wide range of desktop and server products, including Linux, Debian and Ubuntu distributions to verify digital certificates. Its widespread deployment is an Achilles heel in the case of a flaw being uncovered, which is exactly what’s happened.

Researchers at Red Hat have discovered that GnuTLS does not correctly handle certain errors that could occur during the verification of an X.509 certificate, causing it to incorrectly report a successful verification. An attacker could use this flaw (CVE-2014-0092) to create a specially crafted and very fake certificate that could be accepted by GnuTLS as valid for a site chosen by the attacker.

In other words, any site or application that uses GnuTLS to authenticate certificates is at risk for exploit.

The news comes just days after Apple patched a similar issue that exposed iOS and OS X users to similar man-in-the-middle attacks. Due to a flaw in authentication logic on iOS and OS X platforms, an attacker can bypass SSL/TLS verification routines upon the initial connection handshake. This enables an adversary to masquerade as coming from a trusted remote endpoint, such as a favorite webmail provider, and perform full interception of encrypted traffic between the user and the destination server, as well as give them a capability to modify the data in flight (such as deliver exploits to take control of a system).

Updated GnuTLS packages that fix the issue are now available for Red Hat Enterprise Linux 6, and a host of others have issued their own fixes. For the update to take effect, all applications linked to the GnuTLS library must be restarted.

For its part, GnuTLS has acknowledged the issue and has issued its own advisory.

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