CVE-2021-41267 Webcache Poisoning in Symfony
Attackers can poison web caches by forging X-Forwarded-Prefix headers in Symfony applications, potentially serving malicious content to users.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-41267?
CVE-2021-41267 is a medium-severity vulnerability in Sensiolabs Symfony, published on 24 Nov 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Symfony/Http-Kernel is the HTTP kernel component for Symfony, a PHP framework for web and console applications and a set of reusable PHP components. Headers that are not part of the "trusted_headers" allowed list are ignored and protect users from "Cache poisoning" attacks. In Symfony 5.2, maintainers added support for the `X-Forwarded-Prefix` headers, but this header was accessible in SubRequest, 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` header, leading to a web cache poisoning issue. Versions 5.3.12 and later have a patch to ensure that the `X-Forwarded-Prefix` header is not forwarded to subrequests when it is not trusted.
Weakness: CWE-444
Which versions are affected by CVE-2021-41267?
5 open source packages ship an affected version, including symfony/http-kernel, symfony and symfony/symfony. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
symfony/http-kernel Packagist | From 5.2.0 | 5.3.12 |
symfony/http-kernel Packagist | From 5.2.0 | 5.3.12 |
symfony Bitnami | From 5.2.0 | 5.3.12 |
symfony/symfony Packagist | From 5.2.0 | 5.3.12 |
symfony/symfony Packagist | From 5.2.0 | 5.3.12 |
Products include Sensiolabs Symfony.
How do I fix CVE-2021-41267?
Upgrade symfony/http-kernel to 5.3.12 or later.
Is CVE-2021-41267 being exploited?
There is no known exploitation of CVE-2021-41267 in the wild and no public exploit code.
Other vulnerabilities in Sensiolabs Symfony
Sources
Also known as BIT-symfony-2021-41267, GHSA-q3j3-w37x-hq2q.