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Improper Output Neutralization for Logs Affecting zookeeper-3.9-advanced-compat package, versions <3.9.6-r0

Severity

 Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.78% (55th percentile)

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  • Snyk IDSNYK-MINIMOSLATEST-ZOOKEEPER39ADVANCEDCOMPAT-19957978
  • published20 Sept 2026
  • disclosed16 Sept 2026
Report a new vulnerability Found a mistake?

Introduced: 16 Sep 2026

NewCVE-2026-84501  (opens in a new tab)
CWE-117  (opens in a new tab)

How to fix?

Upgrade Minimos:latest zookeeper-3.9-advanced-compat to version 3.9.6-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream zookeeper-3.9-advanced-compat package and not the zookeeper-3.9-advanced-compat package as distributed by Minimos. See How to fix? for Minimos:latest relevant fixed versions and status.

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.