Apache ZooKeeper: Audit log injection via unsanitized output from multiple sources

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-84439
StatePUBLISHED
Assignerapache
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 10:16:53 UTC
Updated2026-09-16 10:16:53 UTC
DescriptionWhen audit logging is enabled (zookeeper.audit.enable=true), an unauthenticated attacker can inject arbitrary fields into Apache ZooKeeper's audit log by sending a digest authentication request with tab characters (\t) embedded in the username. Because the audit log uses tab-separated key=value format, the injected tabs are parsed as legitimate field separators, allowing the attacker to spoof audit results (e.g., injecting result=success), forge operation types, and corrupt forensic evidence. A log injection vulnerability in Apache ZooKeeper allows a client that can call setACL to inject forged key-value fields into zookeeper_audit.log. When audit logging is enabled, the server serializes attacker-controlled digest ACL ids into the acl= audit field without escaping tab characters. Because audit events are emitted as tab-separated key=value records, a crafted ACL id can make one successful setAcl event appear to contain forged fields such as operation=delete and znode=/forged. This undermines the integrity of downstream audit parsing, alerting, and incident response. 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 3.9.6 or 3.8.7, which fixes the issue.

Risk And Classification

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

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
lists.apache.org/thread/b7qnjvqjh393l0j07tmnb5ggg40sx3m6 [email protected] lists.apache.org
www.openwall.com/lists/oss-security/2026/09/15/6 ADP www.openwall.com
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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