Upon receiving each incoming request header data, Envoy will iterate...

Vulnerability Description

Upon receiving each incoming request header data, Envoy will iterate over existing request headers to verify that the total size of the headers stays below a maximum limit. The implementation in versions 1.10.0 through 1.11.1 for HTTP/1.x traffic and all versions of Envoy for HTTP/2 traffic had O(n^2) performance characteristics. A remote attacker may craft a request that stays below the maximum request header size but consists of many thousands of small headers to consume CPU and result in a denial-of-service attack.

References

• https://github.com/envoyproxy/envoy/commits/master
• https://github.com/envoyproxy/envoy/commit/afc39bea36fd436e54262f150c009e8d72db5014
• https://github.com/envoyproxy/envoy/issues/8520