How severe is CVE-2015-4050?

No CVSS score has been assigned to CVE-2015-4050 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2015-4050?

CVE-2015-4050 affects the following packages: symfony/http-kernel (Packagist), symfony/http-kernel (Packagist), symfony/http-kernel (Packagist), symfony/symfony (Packagist), symfony/symfony (Packagist), symfony/symfony (Packagist), symfony/symfony (Packagist), symfony/http-kernel (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2015-4050?

Update symfony/http-kernel to 2.3.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-4050 is resolved across your whole dependency graph.

How do I detect CVE-2015-4050 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/http-kernel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2015-4050 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2015-4050?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2015-4050 can be triaged on real exposure rather than presence alone.

Is CVE-2015-4050 actively exploited in the wild?

No public exploit code has been indexed for CVE-2015-4050 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2015-4050?

CVE-2015-4050 has an EPSS (Exploit Prediction Scoring System) score of 8.2%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2015-4050?

CVE-2015-4050 is classified as CWE-284 (CWE-284). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2015-4050?

A Nuclei detection template exists for CVE-2015-4050, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2015-4050 published, and has it been updated?

CVE-2015-4050 was published on June 2, 2015 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2015-4050 — symfony/http-kernel

CVE-2015-4050 is a CWE-284 vulnerability in symfony/http-kernel. A fix is available for symfony/http-kernel — see the affected versions and patch details below.

Symfony Incorrect Access Control

Also known asGHSA-qmqw-mpqp-mr54

Published

Jun 2, 2015

Updated

Apr 10, 2026

Affected

8 pkgs

Patched

6 / 8

Exploits

None indexed

Exploitation data as of Sep 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

8.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs95th percentile — riskier than 95% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

8 pkgs affected

🐘symfony/http-kernel🐘symfony/http-kernel🐘symfony/http-kernel🐘symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/symfony🐘symfony/http-kernel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

FragmentListener in the HttpKernel component in Symfony 2.3.19 through 2.3.28, 2.4.9 through 2.4.10, 2.5.4 through 2.5.11, and 2.6.0 through 2.6.7, when ESI or SSI support enabled, does not check if the _controller attribute is set, which allows remote attackers to bypass URL signing and security rules by including (1) no hash or (2) an invalid hash in a request to /_fragment.

This issue has been fixed in Symfony 2.3.29, 2.5.12, and 2.6.8. Note that no fixes are provided for Symfony 2.4 as it's not maintained anymore.

Affected Packages

8 total 6 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`symfony/http-kernel`	≥ 2.3.19&&< 2.3.29	2.3.29`composer require symfony/http-kernel:^2.3.29`
🐘Packagist	`symfony/http-kernel`	≥ 2.5.4&&< 2.5.12	2.5.12`composer require symfony/http-kernel:^2.5.12`
🐘Packagist	`symfony/http-kernel`	≥ 2.6.0&&< 2.6.8	2.6.8`composer require symfony/http-kernel:^2.6.8`
🐘Packagist	`symfony/symfony`	≥ 2.3.19&&< 2.3.29	2.3.29`composer require symfony/symfony:^2.3.29`
🐘Packagist	`symfony/symfony`	≥ 2.4.9	No fix
🐘Packagist	`symfony/symfony`	≥ 2.5.4&&< 2.5.12	2.5.12`composer require symfony/symfony:^2.5.12`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symfony/http-kernel, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update symfony/http-kernel to 2.3.29 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-4050 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2015-4050 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2015-4050. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

How to detect CVE-2015-4050

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2015-4050 -u https://target

Template: Symfony - Authentication Bypass
Severity: medium
Impact: Successful exploitation of this vulnerability could allow an attacker to bypass authentication and gain unauthorized access to the affected system.
Remediation: Apply the latest security patches or upgrade to a non-vulnerable version of Symfony.

Template by ProjectDiscovery nuclei-templates (ELSFA7110, meme-lord), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

FragmentListener in the HttpKernel component in Symfony 2.3.19 through 2.3.28, 2.4.9 through 2.4.10, 2.5.4 through 2.5.11, and 2.6.0 through 2.6.7, when ESI or SSI support enabled, does not check if the `_controller` attribute is set, which allows remote attackers to bypass URL signing and security rules by including (1) no hash or (2) an invalid hash in a request to `/_fragment`. This issue has been fixed in Symfony 2.3.29, 2.5.12, and 2.6.8. Note that no fixes are provided for Symfony 2.4 as it's not maintained anymore.

O3 Security · Impact-Aware SCA

Is CVE-2015-4050 in your dependencies?

O3 Security finds CVE-2015-4050 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works