CVE-2026-84501Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider
Updated under an hour ago ()
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It affects Apache Software Foundation Apache ZooKeeper and 1 other product. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 5.3 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Weakness (CWE)
- CWE-117
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- apache
- NVD analysis
- Analyzed
- Record last updated
- Sep 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Apache Software Foundation Apache ZooKeeper apache_software_foundation:apache_zookeeper (from the name) | from 3.9.0 through 3.9.5; from 3.8.0 through 3.8.6 | CNA record |
apache zookeeper apache:zookeeper | from 3.8.0 before 3.8.7; from 3.9.0 before 3.9.6 | NVD |
References
- https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33yvendor-advisory, mailing-list
- http://www.openwall.com/lists/oss-security/2026/09/15/7mailing-list
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.