{"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 ..."}