{"id":"CVE-2026-84501","title":"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)","summary":"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, Ense…","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":"2026-09-18T14:36:51.747","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-84501","references":[{"url":"https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y","label":"security@apache.org"},{"url":"http://www.openwall.com/lists/oss-security/2026/09/15/7","label":"af854a3a-2127-422b-91ae-364da2661108"}],"tags":["nvd","cve.org"],"epss":0.00781,"epssPercentile":0.54023,"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-16T19:42:27.138755Z"},"ingestedAt":"2026-09-16T09:53:11.603Z","slug":"CVE-2026-84501","body":"## Overview\n\nAn 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.\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 3.8.7 or 3.9.6, 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":0.2,"exploitation":0,"ransomware":0},"changes":[{"seq":205697,"id":"CVE-2026-84501","ts":1789589105896,"field":"cvss","old":null,"new":"5.3"},{"seq":205696,"id":"CVE-2026-84501","ts":1789589105896,"field":"severity","old":"none","new":"medium"}]}