BGP Route Leak.

An unintended BGP propagation in which an autonomous system advertises routes outside the intended business relationship, often steering global traffic into the wrong AS. It belongs to the Network Security category of cybersecurity.

An unintended BGP propagation in which an autonomous system advertises routes outside the intended business relationship, often steering global traffic into the wrong AS.

A route leak, formally categorized in RFC 7908, occurs when an AS advertises routes it learned from one neighbor to another neighbor in a way that violates the local routing policy (typically the Gao-Rexford model: customer, provider, peer). Unlike a deliberate hijack, route leaks are usually misconfigurations of route maps, prefix lists, or BGP confederation/community handling. The effect is similar to a hijack: traffic for prefixes is funneled through the leaking AS, which is often undersized, causing congestion, packet loss, and exposure of traffic to interception. High-profile examples include the 2017 Google/NTT incident in Japan and the 2019 Verizon/DQE leak. Mitigations include RFC 9234 BGP Roles, RPKI ASPA, peer-locking, and outbound prefix filters.

Defences for BGP Route Leak typically combine technical controls and operational practices, as detailed in the full definition above.

Common alternative names include: BGP route leakage, Routing policy violation.