A flaw was found in Envoy 1.9.0 and older. When parsing HTTP/1.x header values, Envoy does not reject embedded zero characters (NUL, ASCII 0x0). This allows remote attackers crafting header values containing embedded NUL characters to potentially bypass header matching rules, gaining access to unauthorized resources.

Upstream issue:

https://github.com/envoyproxy/envoy/issues/6434

References:

https://istio.io/blog/2019/announcing-1.1.2/

A flaw was found in Envoy 1.9.0 and older. Envoy does not normalize HTTP URL paths. A remote attacker may craft a path with a relative path, e.g. something/../admin, to bypass access control, e.g. a block on /admin. A backend server could then interpret the unnormalized path and provide an attacker access beyond the scope provided for by the access control policy.

Upstream issue:

https://github.com/envoyproxy/envoy/issues/6435

References:

https://istio.io/blog/2019/announcing-1.1.2/

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.