{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*",
            "extracted_events": [
              {
                "introduced": "3.8.0"
              },
              {
                "fixed": "3.8.7"
              },
              {
                "introduced": "3.9.0"
              },
              {
                "fixed": "3.9.6"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "97c181a40d6dd6ccb2fdad7fcdbd1fd74ab0b6c8"
            },
            {
              "fixed": "9085db92dd679e1e90a63bfe6ae6345ab6cbc4ae"
            },
            {
              "introduced": "1674a5e97f43bc38e9bf56b04f83a7ae34d68249"
            },
            {
              "fixed": "a355171b081b5b60749db8f19cca1528b0df936f"
            }
          ],
          "repo": "https://github.com/apache/zookeeper",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "apache",
    "cwe_ids": [
      "CWE-117"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84501.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "3.9.0"
          },
          {
            "last_affected": "3.9.5"
          },
          {
            "introduced": "3.8.0"
          },
          {
            "last_affected": "3.8.6"
          }
        ],
        "source": "AFFECTED_FIELD"
      },
      {
        "extracted_events": [
          {
            "introduced": "3.9.0"
          },
          {
            "fixed": "3.9.5"
          },
          {
            "introduced": "3.8.0"
          },
          {
            "fixed": "3.8.6"
          }
        ],
        "source": "DESCRIPTION"
      }
    ]
  },
  "details": "An unauthenticated attacker can inject arbitrary fake log lines into Apache ZooKeeper's operational log by sending a crafted add_auth(\"ensemble\", ...) request containing newline characters (\\n). When the ensemble name doesn't match, EnsembleAuthenticationProvider.handleAuthentication() logs the raw, unsanitized name via LOG.warn(). Because SLF4J's {} placeholder preserves embedded newlines, the attacker can forge complete log entries — with arbitrary timestamps, log levels, class names, and messages — that are visually indistinguishable from genuine ZooKeeper log output.\n\nThis issue affects Apache ZooKeeper: from 3.9.0 through 3.9.5, from 3.8.0 through 3.8.6.\n\nUsers are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.",
  "id": "CVE-2026-84501",
  "modified": "2026-09-20T11:30:21.134760751Z",
  "published": "2026-09-16T09:28:10.294Z",
  "references": [
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/15/7"
    },
    {
      "type": "WEB",
      "url": "https://repo.maven.apache.org/maven2"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84501.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-84501"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider"
}