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CVE-2015-4050

25
FAUCET Score

CVE-2015-4050 describes an authentication bypass vulnerability in the FragmentListener component of Symfony versions 2.3.19-2.3.28, 2.4.9-2.4.10, 2.5.4-2.5.11, and 2.6.0-2.6.7, specifically when ESI or SSI support is enabled. This medium-severity vulnerability (CVSS 4.3) allows remote attackers to bypass URL signing and security rules by sending requests to /_fragment with missing or invalid hashes, leading to potential unauthorized access. While not listed in CISA's KEV catalog, there is a Nuclei template available for detection and it has garnered some community discussion and media coverage, indicating awareness and potential for exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
2.3.19CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:2.3.19:*:*:*:*:*:*:*
2.3.20CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:2.3.20:*:*:*:*:*:*:*
2.3.21CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:2.3.21:*:*:*:*:*:*:*
2.3.22CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:2.3.22:*:*:*:*:*:*:*
2.3.23CPE matchmatch criteria
cpe:2.3:a:sensiolabs:symfony:2.3.23:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

4.3MEDIUM

AV:N/AC:M/Au:N/C:N/I:P/A:N

Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
Access Vector
NETWORK
Access Complexity
MEDIUM
Authentication
NONE
Exploitability Score
8.6
Impact Score
2.9
CvssVersion
2.0

Exploit Intelligence

EPSS Score
8.27%
Probability of exploitation in next 30 days
EPSS Percentile
94.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2015-4050 · Aug 30, 2021
This CVE's current EPSS score of 0.0827 is in the 94th percentile among its peer group of 19,958 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

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

Remediation

Patch Available

Vendor Patches (6)

composerpatch availablevia ghsa
Product: symfony/http-kernelFixed in: 2.3.29
composerpatch availablevia ghsa
Product: symfony/http-kernelFixed in: 2.5.12
composerpatch availablevia ghsa
Product: symfony/http-kernelFixed in: 2.6.8
composerpatch availablevia ghsa
Product: symfony/symfonyFixed in: 2.3.29
composerpatch availablevia ghsa
Product: symfony/symfonyFixed in: 2.5.12
composerpatch availablevia ghsa
Product: symfony/symfonyFixed in: 2.6.8

Vendor Advisories (1)

composerGHSA-qmqw-mpqp-mr54medium

Symfony Incorrect Access Control

May 17, 2022

References

lists.fedoraproject.org / pipermail/package-announce/2015-June/159513.html
lists.fedoraproject.org / pipermail/package-announce/2015-June/159603.html
lists.fedoraproject.org / pipermail/package-announce/2015-June/159610.html
symfony.com / blog/cve-2015-4050-esi-unauthorized-access
Vendor Advisory
debian.org / security/2015/dsa-3276
securityfocus.com / bid/74928