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CVE-2026-84501

Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider

Published: Sep 16, 2026Updated: Sep 18, 2026 Sources: CVE List NVDCWE-117
5.3MEDIUM
NVD MITRE
EPSS Score
0.8%
Top 45.6%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:LA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:LIntegrity
Low
A:NAvailability
None
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Weaknesses

CWE-117

Affected Products

apache
oss-project·USaka apache http server, apache httpd
zookeeperOn-premDatabase
Databases / cache-message-queue
Apache Software Foundation
oss-project·USaka apache foundation
Apache ZooKeeperOn-premWeb App
Databases / cache-message-queue

Exploitability

Official Patch Available

References

https://lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y
lists.apache.org
http://www.openwall.com/lists/oss-security/2026/09/15/7
openwall.com

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