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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | symfony | 2.7.0~beta2+dfsg-2 | — |
| Debian 13 | symfony | 2.7.0~beta2+dfsg-2 | — |
| Debian 12 | symfony | 2.7.0~beta2+dfsg-2 | — |
| Debian 8 | symfony | 2.3.21+dfsg-4+deb8u1 | DSA-3276-1 |
Automated scanner template
A ready-made Nuclei template detects this vulnerability automatically. Vulnerabilities with public scanner templates are typically probed across the internet soon after the template appears — exposed systems should be patched first.
- Symfony - Authentication Bypass http/cves/2015/CVE-2015-4050.yaml
Source: projectdiscovery/nuclei-templates (MIT) — updated daily. Only links are listed.
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Packagist | symfony/http-kernel | >= 2.3.19, < 2.3.29 | 2.3.29 | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/http-kernel | >= 2.5.4, < 2.5.12 | 2.5.12 | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/http-kernel | >= 2.6.0, < 2.6.8 | 2.6.8 | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/http-kernel | >= 2.4.9, <= 2.4.10 | — | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/symfony | >= 2.3.19, < 2.3.29 | 2.3.29 | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/symfony | >= 2.4.9, <= 2.4.10 | — | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/symfony | >= 2.5.4, < 2.5.12 | 2.5.12 | GHSA-qmqw-mpqp-mr54 |
| Packagist | symfony/symfony | >= 2.6.0, < 2.6.8 | 2.6.8 | GHSA-qmqw-mpqp-mr54 |
Advisories 1
- DSA-3276-1 symfony - security update Debian Security (DSA / DLA) · Mar 9, 2026
References
- http://symfony.com/blog/cve-2015-4050-esi-unauthorized-access
- FEDORA-2015-9039 vendor-advisory
- DSA-3276 vendor-advisory
- FEDORA-2015-9034 vendor-advisory
- FEDORA-2015-9025 vendor-advisory
- 74928 vdb-entry