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CVE-2021-41267

23
FAUCET Score

CVE-2021-41267 is a web cache poisoning vulnerability affecting Symfony/Http-Kernel versions prior to 5.3.12. It arises from improper handling of the X-Forwarded-Prefix header in subrequests, even when not explicitly trusted. This medium severity vulnerability (CVSS 6.5) allows an unauthenticated attacker to inject malicious data into the web cache, potentially impacting other users. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 5.2.0, < 5.3.12CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.24%
Probability of exploitation in next 30 days
EPSS Percentile
66.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0124 is in the 79th percentile among its peer group of 26,236 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

composerpatch availablevia ghsa
Product: symfony/http-kernelFixed in: 5.3.12
composerpatch availablevia ghsa
Product: symfony/symfonyFixed in: 5.3.12
github_advisorypatch availablevia nvd_reference
View patch

Vendor Advisories (1)

composerGHSA-q3j3-w37x-hq2qmedium

Webcache Poisoning in symfony/http-kernel

Nov 24, 2021

References

github.com / symfony/symfony/commit/95dcf51682029e89450aee86267e3d553aa7c487
PatchThird Party Advisory
github.com / symfony/symfony/pull/44243
PatchThird Party Advisory
github.com / symfony/symfony/releases/tag/v5.3.12
Release NotesThird Party Advisory
github.com / symfony/symfony/security/advisories/GHSA-q3j3-w37x-hq2q
PatchThird Party Advisory