CVE-2026-84501 Details
Description
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.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Sep 16, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| http://www.openwall.com/lists/oss-security/2026/09/15/7 | CVE | Mailing List |
| https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y | [email protected] | Mailing ListVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-117 | Improper Output Neutralization for Logs | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| apache zookeeper | >= 3.8.0, < 3.8.7 >= 3.9.0, < 3.9.6 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 18, 2026 | Initial Analysis | [email protected] |
| Sep 16, 2026 | CVE Modified | CISA-ADP |
| Sep 16, 2026 | CVE Modified | CVE |
| Sep 16, 2026 | New CVE Received | [email protected] |