{
  "crds_version": "0.1",
  "kind": "base",
  "id": "crds:cve-2021-26084",
  "revision": 1,
  "title": "Confluence Server & Data Center — OGNL Injection (2021)",
  "summary": "Older Confluence Server and Data Center releases evaluate attacker-supplied text as program code, letting an unauthenticated visitor execute commands on the wiki server. Ransomware crews are known to use it.",
  "source_type": "cve",
  "severity": "critical",
  "cvss": {
    "score": 9.8,
    "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "version": "3.1"
  },
  "epss": 0.99999,
  "exploitation": {
    "known_exploited": true,
    "exploit_available": true,
    "attack_complexity": "low",
    "kev_added": "2021-11-03",
    "prerequisites": "Network access to a self-hosted Confluence instance in an affected version range. No credentials needed."
  },
  "remediation": {
    "patch_available": true,
    "fixed_in": [
      "Confluence 6.13.23",
      "Confluence 7.4.11",
      "Confluence 7.11.6",
      "Confluence 7.12.5"
    ]
  },
  "mitre_attack": [
    "T1190"
  ],
  "kill_chain": "initial_access",
  "recommended_action": "Update Confluence to 6.13.23, 7.4.11, 7.11.6 or 7.12.5; if the instance ever faced the internet unpatched, hunt for web shells and stray processes before declaring it clean.",
  "confidence": "high",
  "provenance": [
    {
      "fields": [
        "title",
        "summary",
        "cvss",
        "severity",
        "exploitation.attack_complexity",
        "exploitation.prerequisites",
        "exploitation.exploit_available",
        "remediation",
        "references"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2021-26084",
      "retrieved_at": "2026-08-07T07:53:55.549Z",
      "confidence": "high",
      "extractor": "claude-code"
    },
    {
      "fields": [
        "exploitation.known_exploited",
        "summary",
        "recommended_action"
      ],
      "source": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "retrieved_at": "2026-08-07T07:53:55.549Z",
      "confidence": "high",
      "extractor": "claude-code"
    },
    {
      "fields": [
        "epss"
      ],
      "source": "https://api.first.org/data/v1/epss?cve=CVE-2021-26084",
      "retrieved_at": "2026-08-07T07:53:55.549Z",
      "confidence": "high",
      "extractor": "claude-code"
    }
  ],
  "references": [
    {
      "type": "cve",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-26084",
      "label": "NVD record"
    },
    {
      "type": "vendor_advisory",
      "url": "https://jira.atlassian.com/browse/CONFSERVER-67940",
      "label": "Atlassian issue CONFSERVER-67940"
    },
    {
      "type": "exploit",
      "url": "http://packetstormsecurity.com/files/167449/Atlassian-Confluence-Namespace-OGNL-Injection.html",
      "label": "Public expression-injection exploit"
    },
    {
      "type": "cisa",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26084",
      "label": "CISA Known Exploited Vulnerabilities entry"
    }
  ],
  "published_at": "2021-08-30T07:15:06.587Z",
  "issued_at": "2026-08-07T07:53:55.549Z",
  "tags": [
    "atlassian",
    "confluence",
    "expression-injection",
    "wiki",
    "kev",
    "ransomware"
  ]
}