CVE-2021-41267

Impact

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](https://github.com/symfony/symfony/commit/95dcf51682029e89450aee86267e3d553aa7c487) for branch 5.3. Credits ------- We would like to thank Soner Sayakci for reporting the issue and Jérémy Derussé for fixing the issue.

Affected packages

Affected products

Weakness classification

References

• NVD record
• CVE.org record
• GitHub advisory
• https://github.com/symfony/symfony/commit/95dcf51682029e89450aee86267e3d553aa7c487
• https://github.com/symfony/symfony/pull/44243
• https://github.com/symfony/symfony/releases/tag/v5.3.12
• https://github.com/symfony/symfony/security/advisories/GHSA-q3j3-w37x-hq2q
• https://github.com/advisories/GHSA-q3j3-w37x-hq2q
• https://nvd.nist.gov/vuln/detail/CVE-2021-41267
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-kernel/CVE-2021-41267.yaml
• https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2021-41267.yaml
• https://symfony.com/cve-2021-41267