GHSA-q3j3-w37x-hq2q Webcache Poisoning in symfony/http-kernel

• Packagist symfony/http-kernel: >= 5.2.0, < 5.3.12 → fixed in 5.3.12 • Packagist symfony/symfony: >= 5.2.0, < 5.3.12 → fixed in 5.3.12

Description ----------- When a Symfony application is running behind a proxy or a load-balancer, you can tell Symfony to look for the `X-Forwarded-*` HTTP headers. HTTP headers that are not part of the "trusted_headers" allowed list are ignored and protect you from "Cache poisoning" attacks. In Symfony 5.2, we've added support for the `X-Forwarded-Prefix` header, but this header was accessible in sub-requests, even if it was not part of the "trusted_headers" allowed list. An attacker could leverage this opportunity to forge requests containing a `X-Forwarded-Prefix` HTTP header, leading to a web cache poisoning issue. Resolution ---------- Symfony now ensures that the `X-Forwarded-Prefix` HTTP header is not forwarded to sub-requests when it is not trusted. The patch for this issue is available here for branch 5.3. Credits ------- We would like to thank Soner Sayakci for reporting the issue and Jérémy Derussé for fixing the issue.