Bug 2535096 (CVE-2026-84501) - CVE-2026-84501 zookeeper: Apache ZooKeeper: Operational log forgery via newline injection
Summary: CVE-2026-84501 zookeeper: Apache ZooKeeper: Operational log forgery via newli...
Keywords:
Status: NEW
Alias: CVE-2026-84501
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2542320 2542321 2542322
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-16 09:49 UTC by OSIDB Bzimport
Modified: 2026-11-04 14:45 UTC (History)
53 users (show)

Fixed In Version:
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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2026:95221 0 None None None 2026-11-04 14:45:52 UTC

Description OSIDB Bzimport 2026-09-16 09:49:04 UTC 
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.
Comment 2 Jon Orris 2026-11-04 14:45:49 UTC 
This issue has been addressed in the following products:

  Red Hat JBoss Enterprise Application Platform 8.1

Via RHSA-2026:95221 https://access.redhat.com/errata/RHSA-2026:95221
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