{"id":"CVE-2026-84439","title":"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 us…","summary":"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 us…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-117"],"vendor":"apache","product":"zookeeper","affected":["zookeeper >= 3.8.0, < 3.8.7","zookeeper >= 3.9.0, < 3.9.6"],"patched":["zookeeper 3.9.6"],"published":"2026-09-16","updated":"2026-09-18","sourceUpdated":"2026-09-18T14:37:30.650","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-84439","references":[{"url":"https://lists.apache.org/thread/b7qnjvqjh393l0j07tmnb5ggg40sx3m6","label":"security@apache.org"},{"url":"http://www.openwall.com/lists/oss-security/2026/09/15/6","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","cve.org"],"epss":0.00742,"epssPercentile":0.52667,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-17T19:14:36.442526Z"},"ingestedAt":"2026-09-16T09:53:11.605Z","slug":"CVE-2026-84439","body":"## Overview\n\nWhen 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.\n\n## Affected\n\n- `zookeeper >= 3.8.0, < 3.8.7`\n- `zookeeper >= 3.9.0, < 3.9.6`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `zookeeper 3.9.6`","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":206523,"id":"CVE-2026-84439","ts":1789673254766,"field":"cvss","old":null,"new":"5.3"},{"seq":206522,"id":"CVE-2026-84439","ts":1789673254766,"field":"severity","old":"none","new":"medium"}]}