cve-2026-84439

{
  "cvss": 5.3,
  "datePublished": "2026-09-16T10:16:53.433",
  "dateUpdated": "2026-09-18T14:37:30.650",
  "description": "When audit logging is enabled (zookeeper.audit.enable=true), an unauthenticated attacker can inject arbitrary fields into Apache ZooKeeper's audit log by sending a digest authentication request with tab characters (\\t) embedded in the username. Because the audit log uses tab-separated key=value format, the injected tabs are parsed as legitimate field separators, allowing the attacker to spoof audit results (e.g., injecting result=success), forge operation types, and corrupt forensic evidence.\n\nA log injection vulnerability in Apache ZooKeeper allows a client that can call setACL to inject forged key-value fields into zookeeper_audit.log. When audit logging is enabled, the server serializes attacker-controlled digest ACL ids into the acl= audit field without escaping tab characters. Because audit events are emitted as tab-separated key=value records, a crafted ACL id can make one successful setAcl event appear to contain forged fields such as operation=delete and znode=/forged. This undermines the integrity of downstream audit parsing, alerting, and incident response.\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 3.9.6 or 3.8.7, which fixes the issue.",
  "id": "CVE-2026-84439",
  "raw": {
    "affected": [
      {
        "affectedData": [
          {
            "collectionURL": "https://repo.maven.apache.org/maven2",
            "defaultStatus": "unaffected",
            "packageName": "org.apache.zookeeper:zookeeper",
            "packageURL": "pkg:maven/org.apache.zookeeper/zookeeper",
            "product": "Apache ZooKeeper",
            "vendor": "Apache Software Foundation",
            "versions": [
              {
                "lessThanOrEqual": "3.9.5",
                "status": "affected",
                "version": "3.9.0",
                "versionType": "maven"
              },
              {
                "lessThanOrEqual": "3.8.6",
                "status": "affected",
                "version": "3.8.0",
                "versionType": "maven"
              }
            ]
          }
        ],
        "source": "security@apache.org"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "4EB0BE5E-6F39-4D77-BBEC-89AE61429E31",
                "versionEndExcluding": "3.8.7",
                "versionStartIncluding": "3.8.0",
                "vulnerable": true
              },
              {
                "criteria": "cpe:2.3:a:apache:zookeeper:*:*:*:*:*:*:*:*",
                "matchCriteriaId": "78E0C560-E216-4628-9131-E8C919D8B937",
                "versionEndExcluding": "3.9.6",
                "versionStartIncluding": "3.9.0",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "When audit logging is enabled (zookeeper.audit.enable=true), an unauthenticated attacker can inject arbitrary fields into Apache ZooKeeper's audit log by sending a digest authentication request with tab characters (\\t) embedded in the username. Because the audit log uses tab-separated key=value format, the injected tabs are parsed as legitimate field separators, allowing the attacker to spoof audit results (e.g., injecting result=success), forge operation types, and corrupt forensic evidence.\n\nA log injection vulnerability in Apache ZooKeeper allows a client that can call setACL to inject forged key-value fields into zookeeper_audit.log. When audit logging is enabled, the server serializes attacker-controlled digest ACL ids into the acl= audit field without escaping tab characters. Because audit events are emitted as tab-separated key=value records, a crafted ACL id can make one successful setAcl event appear to contain forged fields such as operation=delete and znode=/forged. This undermines the integrity of downstream audit parsing, alerting, and incident response.\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 3.9.6 or 3.8.7, which fixes the issue."
      }
    ],
    "id": "CVE-2026-84439",
    "lastModified": "2026-09-18T14:37:30.650",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          },
          "exploitabilityScore": 3.9,
          "impactScore": 1.4,
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "type": "Secondary"
        }
      ],
      "ssvcV203": [
        {
          "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "ssvcData": {
            "id": "CVE-2026-84439",
            "options": [
              {
                "exploitation": "none"
              },
              {
                "automatable": "yes"
              },
              {
                "technicalImpact": "partial"
              }
            ],
            "role": "CISA Coordinator",
            "timestamp": "2026-09-17T19:14:36.442526Z",
            "version": "2.0.3"
          }
        }
      ]
    },
    "published": "2026-09-16T10:16:53.433",
    "references": [
      {
        "source": "security@apache.org",
        "tags": [
          "Mailing List",
          "Vendor Advisory"
        ],
        "url": "https://lists.apache.org/thread/b7qnjvqjh393l0j07tmnb5ggg40sx3m6"
      },
      {
        "source": "af854a3a-2127-422b-91ae-364da2661108",
        "tags": [
          "Mailing List",
          "Vendor Advisory"
        ],
        "url": "http://www.openwall.com/lists/oss-security/2026/09/15/6"
      }
    ],
    "sourceIdentifier": "security@apache.org",
    "vulnStatus": "Analyzed",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-117"
          }
        ],
        "source": "security@apache.org",
        "type": "Secondary"
      }
    ]
  },
  "severity": "MEDIUM",
  "source": "nvd",
  "title": "When audit logging is enabled (zookeeper.audit.enable=true), an unauthenticated attacker can inject arbitrary fields ..."
}