Vulnerability Note VU#929656

The Border Gateway Protocol (BGP, RFC 4271) is a widely used inter-Autonomous System routing protocol. BGP communication among peer routers is critical to the stable operation of the internet. Multiple vendors BGP implementations do not properly handle specially crafted BGP UPDATE messages. A vulnerable BGP implementation could drop sessions when processing crafted UPDATE messages. A persistent attack could lead to routing instability (route flapping). To affect a BGP session, an attacker would need to succesfully inject a specially crafted packet into an existing BGP session or the underlying TCP session (179/tcp). In other words, the attacker would need to have a valid, configured BGP session or be able to spoof TCP traffic.

This vulnerability was first announced as affecting Juniper routers. Further investigation indicates that other vendors are affected by the same or similar issues. Please see the Systems Affected section below.

A remote attacker could cause a denial of service by injecting a specially crafted BGP UPDATE message into a legitimate BGP session. An attacker with a configured BGP session could attack targets several BGP hops away, or an attacker could spoof TCP traffic.

Upgrade
Upgrade your BGP software as appropriate. Please see the Systems Affected section below for information about specific vendors.

In order to send a specially crafted BGP UPDATE message, an attacker must have or spoof a valid BGP connection. The following workarounds and other BGP security techniques may provide some defense against spoofed connections, however spoofed connections may not be a realistic threat scenario, and the more correct resolution is to upgrade.

Authenticate BGP Traffic

Use TCP MD5 to authenticate BGP traffic (RFC 2385). Only allow BGP traffic from authorized peers. It is generally recognized that TCP MD5

Restrict BGP Access

Restrict BGP network access to authorized peers. If possible, run BGP on management networks, not transit networks. More information about BGP security (including secure BGP configuration templates) is available from the Team Cymru Reading Room.