{"id":"UBUNTU-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":"2026-10-17T12:56:16.118970050Z","published":"2026-09-16T10:16:00Z","upstream":["CVE-2026-84501"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-84501"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-84501"}],"affected":[{"package":{"name":"zookeeper","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/zookeeper?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.5+dfsg-1","3.4.5+dfsg-1ubuntu0.1~esm1","3.4.5+dfsg-1ubuntu0.1~esm3"],"ecosystem_specific":{"binaries":[{"binary_name":"libzookeeper-java","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"libzookeeper-mt2","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"libzookeeper-st2","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"libzookeeper2","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"python-zookeeper","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"zookeeper","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"zookeeper-bin","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"},{"binary_name":"zookeeperd","binary_version":"3.4.5+dfsg-1ubuntu0.1~esm3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/zookeeper?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.6-8","3.4.7-1","3.4.8-1","3.4.8-1ubuntu0.1~esm1","3.4.8-1ubuntu0.1~esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"3.4.8-1ubuntu0.1~esm2","binary_name":"libzookeeper-java"},{"binary_name":"libzookeeper-mt2","binary_version":"3.4.8-1ubuntu0.1~esm2"},{"binary_name":"libzookeeper-st2","binary_version":"3.4.8-1ubuntu0.1~esm2"},{"binary_version":"3.4.8-1ubuntu0.1~esm2","binary_name":"libzookeeper2"},{"binary_version":"3.4.8-1ubuntu0.1~esm2","binary_name":"python-zookeeper"},{"binary_name":"zookeeper","binary_version":"3.4.8-1ubuntu0.1~esm2"},{"binary_name":"zookeeper-bin","binary_version":"3.4.8-1ubuntu0.1~esm2"},{"binary_name":"zookeeperd","binary_version":"3.4.8-1ubuntu0.1~esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/zookeeper?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.10-2","3.4.10-3","3.4.13-3","3.4.13-3ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.4.13-3ubuntu0.1~esm1","binary_name":"libzookeeper-java"},{"binary_version":"3.4.13-3ubuntu0.1~esm1","binary_name":"libzookeeper-mt2"},{"binary_version":"3.4.13-3ubuntu0.1~esm1","binary_name":"libzookeeper-st2"},{"binary_name":"python-zookeeper","binary_version":"3.4.13-3ubuntu0.1~esm1"},{"binary_name":"zookeeper","binary_version":"3.4.13-3ubuntu0.1~esm1"},{"binary_name":"zookeeper-bin","binary_version":"3.4.13-3ubuntu0.1~esm1"},{"binary_name":"zookeeperd","binary_version":"3.4.13-3ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/zookeeper?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.13-1","3.4.13-3","3.4.13-3build1","3.4.13-4","3.4.13-5","3.4.13-5build1","3.4.13-5ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_version":"3.4.13-5ubuntu0.1","binary_name":"libzookeeper-java"},{"binary_version":"3.4.13-5ubuntu0.1","binary_name":"libzookeeper-mt2"},{"binary_name":"libzookeeper-st2","binary_version":"3.4.13-5ubuntu0.1"},{"binary_name":"python3-zookeeper","binary_version":"3.4.13-5ubuntu0.1"},{"binary_name":"zookeeper","binary_version":"3.4.13-5ubuntu0.1"},{"binary_version":"3.4.13-5ubuntu0.1","binary_name":"zookeeper-bin"},{"binary_name":"zookeeperd","binary_version":"3.4.13-5ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-84501.json"}},{"package":{"name":"zookeeper","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/zookeeper?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.4.13-5ubuntu4","3.4.13-6ubuntu2","3.4.13-6ubuntu3","3.4.13-6ubuntu4","3.4.13-6ubuntu4.1"],"ecosystem_specific":{"binaries":[{"binary_name":"libzookeeper-java","binary_version":"3.4.13-6ubuntu4.1"},{"binary_version":"3.4.13-6ubuntu4.1","binary_name":"libzookeeper-mt2"},{"binary_name":"libzookeeper-st2","binary_version":"3.4.13-6ubuntu4.1"},{"binary_version":"3.4.13-6ubuntu4.1","binary_name":"python3-zookeeper"},{"binary_version":"3.4.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