Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-84501
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 10:16:53 UTC
Updated2026-09-18 14:36:51 UTC
DescriptionAn 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS: 0.002250000 probability, percentile 0.133760000 (date 2026-09-16)

Problem Types: CWE-117 | CWE-117 CWE-117 Improper output neutralization for logs

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Apache Zookeeper All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Apache Software Foundation Apache ZooKeeper affected 3.9.0 3.9.5 maven Not specified
CNA Apache Software Foundation Apache ZooKeeper affected 3.8.0 3.8.6 maven Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/09/15/7 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com Mailing List
lists.apache.org/thread/ohby1g6zjt72p0w79rhbr41nczzvr33y [email protected] lists.apache.org Mailing List, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Youlong Chen Institute of Computing Technology <[email protected]> (en)

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