{"id":"DEBIAN-CVE-2026-84501","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.  This issue affects Apache ZooKeeper: from 3.9.0 through 3.9.5, from 3.8.0 through 3.8.6.  Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.","modified":"2026-09-26T16:00:09.633607242Z","published":"2026-09-16T10:16:53.557Z","upstream":["CVE-2026-84501"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-84501"}],"affected":[{"package":{"name":"zookeeper","ecosystem":"Debian:12","purl":"pkg:deb/debian/zookeeper?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.8.0-11","3.8.0-11+deb12u1","3.8.0-11+deb12u2","3.9.1-1","3.9.2-1","3.9.2-2","3.9.3-1","3.9.3-2","3.9.4-1","3.9.4-2","3.9.5-1","3.9.5-2","3.9.6-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Debian:13","purl":"pkg:deb/debian/zookeeper?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.9.3-1","3.9.3-1+deb13u1","3.9.3-2","3.9.4-1","3.9.4-2","3.9.5-1","3.9.5-2","3.9.6-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Debian:14","purl":"pkg:deb/debian/zookeeper?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.9.6-1"}]}],"versions":["3.9.3-1","3.9.3-2","3.9.4-1","3.9.4-2","3.9.5-1","3.9.5-2"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-84501.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}