CVE-2021-41267Webcache Poisoning in Symfony
- 6.5MediumCVSS base score
- 1.3%Exploitation in 30 daysEPSS · top 30% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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.
Timeline
ID reserved
By GitHub_M
- 2 months later
· 2 months later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N |
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N |
- EPSS (exploitation in 30 days)
- 1.3% · top 30% of all CVEs (14 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Packagistsymfony/http-kernelGHSA-q3j3-w37x-hq2q (opens in a new tab)
- Packagistsymfony/symfonyGHSA-q3j3-w37x-hq2q (opens in a new tab)
References
References4
- https://github.com/symfony/symfony/pull/44243 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/symfony/symfony/releases/tag/v5.3.12 (opens in a new tab)x_refsource_MISCx_transferred
- https://github.com/symfony/symfony/security/advisories/GHSA-q3j3-w37x-hq2q (opens in a new tab)x_refsource_CONFIRMx_transferred
- https://github.com/symfony/symfony/commit/95dcf51682029e89450aee86267e3d553aa7c487 (opens in a new tab)x_refsource_MISCx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-2377 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-q3j3-w37x-hq2q (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-41267)Record last updated .