CVE-2021-41267: Webcache Poisoning via X-Forwarded-Prefix and sub-request

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.

                Sponsor the Symfony project.

https://symfony.com/blog/cve-2021-41267-webcache-poisoning-via-x-forwarded-prefix-and-sub-request?utm_source=Symfony%20Blog%20Feed&utm_medium=feed

Utworzony 3y | 24 lis 2021, 09:20:08


Zaloguj się, aby dodać komentarz

Inne posty w tej grupie

New in Symfony 7.3: Assets Pre-Compression

Contributed by Kévin Dunglas in

23 kwi 2025, 08:20:31 | Symfony
SymfonyOnline June 2025: Inside a Financial App Breach: Debugging a Million-Dollar Bug

SymfonyOnline June 2025 is almost here, starting in almost 2 months on:

June 10-11: Workshop days. It is possible to attend 1 two-day training or 2 one-day trainings. June 12-13: Online confe

22 kwi 2025, 13:50:03 | Symfony
New in Symfony 7.3: Invokable Commands and Input Attributes

This is the first article in a series showcasing the most important new features introduced by Symfony 7.3, which will be released at the end of May 2025.

22 kwi 2025, 09:10:36 | Symfony
A Week of Symfony #955 (April 14–20, 2025)

This week, the upcoming Symfony 7.3 version improved the AsAlias attribute by adding a new argument, introduced Clock support for UriSigner, and refined the return type of the ContainerInterface::get(

20 kwi 2025, 08:30:06 | Symfony
SymfonyOnline June 2025: Rethinking File Handling in Symfony

SymfonyOnline June 2025 is almost here, starting in almost 2 months on:

June 10-11: Workshop days. It is possible to attend 1 two-day training or 2 one-day trainings. June 12-13: Online confe

16 kwi 2025, 16:30:02 | Symfony
SymfonyLive Paris 2025: Recap and replay!

SymfonyLive Paris 2025 took place three weeks ago — a big thank you to everyone who joined us! The conference was held entirely in French, and now you can relive the best moments: replays, hig

15 kwi 2025, 14:50:24 | Symfony
A Week of Symfony #954 (April 7–13, 2025)

This week, Symfony 7.3 entered its "feature freeze" period in preparation for its release at the end of May 2025. Development activity focused on refining and polishing its new features, including a n

13 kwi 2025, 09:40:02 | Symfony