Cisco IPv6 processing bug can cause DoS attacks

[Aerosol]

Cisco has announced that NCS 6000 and Carrier Routing System (CRS-X) – heavy hunks of iron used in the service provider market – have an IPv6 software bug that needs patching.

The bug impacts the ways Cisco IOS XR units parse IPv6 packets and an attack exploiting the problem could result in a forced restart of the line card that's processing the traffic.

“An attacker could exploit this vulnerability by sending a malformed IPv6 packet, carrying extension headers, through an affected Cisco IOS XR device line card,” the company's advisory states. “This vulnerability could be exploited repeatedly to cause an extended DoS condition.”

Of course, it's only a problem if you're actually processing IPv6 traffic using the vulnerable IOS XR software. It's also restricted to traffic that's transiting the affected device: traffic transiting the device on the way somewhere else won't trigger the bug.

For the Cisco NCS 6000, all versions of the IOS XR software except 5.3.2 are affected. For IOS XR for CRS-X, all versions that support CRS-X line cards, including the 400 Gbps Modular Service Card (MSC) and 400 Gbps Forwarding Processor Cards, the safe version is 5.3.0 – all other versions are vulnerable.

The bug has been designated CVE-2015-0618.

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