Envoy through 1.15.0 only considers the first value when multiple header values are present for some HTTP headers. Envoy’s setCopy() header map API does not replace all existing occurences of a non-inline header.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-25017
Reference (s):
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-2v25-cjjq-5f4w
- https://groups.google.com/forum/#!forum/envoy-security-announce