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Fencer Vulns
medium 5.3

CVE-2026-84501 json

Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider

published 2026-09-16 54 d ago modified 2026-09-19 51 d ago also BIT-zookeeper-2026-84501 , EUVD-2026-80334

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

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, 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.

Patch / fix

  • bitnami zookeeper 3.8.7, 3.9.6
  • apache zookeeper 3.8.7, 3.9.6
  • zookeeper Debian 14 3.9.6-1

debian advisories DEBIAN-CVE-2026-84501

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-84501 updated cvss 5.3

zookeeper: Apache ZooKeeper: Operational log forgery via newline injection

  • Red Hat AMQ Broker 7 parent, zookeeper, zookeeper-jute Red Hat build of Apache Camel for Spring Boot 4 flink-shaded-zookeeper-3, flink-shaded-zookeeper-parent
    affected: workaround, no fix available “Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.”
  • Red Hat Fuse 7 zookeeper, zookeeper-jute, camel-zookeeper, camel-zookeeper-master, org.linkedin.zookeeper-impl
    affected: workaround, no fix planned “Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.”
  • Red Hat JBoss Enterprise Application Platform Expansion Pack parent, zookeeper Red Hat Offline Knowledge Portal offline-knowledge-portal/rhokp-rhel9
    affected: workaround, no fix available “Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-modelmesh-rhel9, rhoai/odh-spark-operator-rhel9, rhoai/odh-th06-cpu-torch210-py312-rhel9, rhoai/odh-th06-cpu-torch291-py312-rhel9, rhoai/odh-th06-rocm64-torch291-py312-rhel9, rhoai/odh-th06-cuda130-torch210-py312-rhel9, +1 more
    affected: workaround, no fix available, no fix planned “Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.”
  • Red Hat JBoss Enterprise Application Platform 8.1
    fixed: vendor fix “Update to Apache ZooKeeper 3.8.7, 3.9.6, or later.” RHSA-2026:95221
  • Red Hat build of Apache Camel 4 for Quarkus 3 flink-shaded-zookeeper-3
    not affected: vulnerable code not in execute path
  • Red Hat JBoss Enterprise Application Platform 8 parent, zookeeper
    not affected: component not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-th-torch-cpu-py312-rhel9, rhoai/odh-th-torch-cuda-py312-rhel9
    not affected: vulnerable code not in execute path
show 1 more
  • Red Hat OpenStack Platform 13 (Queens) puppet-zookeeper Red Hat OpenStack Platform 16.2 puppet-zookeeper
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
53 d ago

Exploit prediction

0.74% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
OSV 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
bitnami zookeeper
>=3.8.0, <3.8.7
>=3.9.0, <3.9.6
3.8.7
3.9.6

Affected products

  • Apache Software Foundation Apache ZooKeeper

Classification

Weakness
  • CWE-117 Improper Output Neutralization for Logs

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.