CVE-2015-4050

Status: ModifiedMedium (4.3)—💥 Exploit

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.

CVSS

Version: 2.0
Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N
Base score: 4.3

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 8.21%
Percentile among all scored CVEs: 95
Score date: 10/7/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

💥 Public exploits

Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.

Nuclei template (automated mass detection) · Symfony - Authentication Bypass

Affected technologies (1)

Sensiolabs — Symfony

CWEs

CWE-284

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2015-4050",
  "cveTags": [],
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        "source": "nvd@nist.gov",
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          "baseScore": 4.3,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:N/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
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      "affectedData": [
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          "vendor": "n/a",
          "product": "n/a",
          "versions": [
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              "status": "affected",
              "version": "n/a"
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  "published": "2015-06-02T14:59:12.253",
  "references": [
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      "url": "http://symfony.com/blog/cve-2015-4050-esi-unauthorized-access",
      "tags": [
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      "source": "cve@mitre.org"
    },
    {
      "url": "http://www.debian.org/security/2015/dsa-3276",
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      "value": "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."
    },
    {
      "lang": "es",
      "value": "FragmentListener en el componente HttpKernel en Symfony 2.3.19 hasta 2.3.28, 2.4.9 hasta 2.4.10, 2.5.4 hasta 2.5.11, y 2.6.0 hasta 2.6.7, cuando ek soporte ESI o SSI está habilitado, no comprueba si el atributo _controller esta configurado, lo que permite a atacantes remotos evadir la firma de URLs y las reglas de seguridad mediante la inclusión de (1) ningún hash o (2) un hash inválido en una solicitud a /_fragment."
    }
  ],
  "lastModified": "2026-06-17T00:26:41.657",
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