SEPTEMBER 18, 2026
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Case File

CVE-2026-84439

MEDIUM · CVSS 5.3 EPSS 0.25%

Source: NVD + CISA KEV + EPSS · Published 2026-09-16 · Last synced 2026-09-18

CyberRota Analysis

AI-Generated

Apache ZooKeeper is vulnerable to a log injection attack that allows unauthenticated clients to manipulate audit logs by injecting tab characters into the username field of digest authentication requests. This exploitation can result in the spoofing of audit results, including the fabrication of operation types and the corruption of forensic evidence, thereby compromising the integrity of audit trails. Organizations using affected versions (3.9.0 to 3.9.5 and 3.8.0 to 3.8.6) should prioritize upgrading to versions 3.9.6 or 3.8.7 to mitigate this risk.

CVE
CVE-2026-84439
Severity
MEDIUM
CVSS
5.3
EPSS
0.25%
Apache

Original NVD Description

When 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.

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