Improper Output Neutralization for Logs Affecting zookeeper-3.8-advanced-compat package, versions <3.8.7-r0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-MINIMOSLATEST-ZOOKEEPER38ADVANCEDCOMPAT-19957950
- published20 Sept 2026
- disclosed16 Sept 2026
Introduced: 16 Sep 2026
NewCVE-2026-84439 (opens in a new tab)How to fix?
Upgrade Minimos:latest zookeeper-3.8-advanced-compat to version 3.8.7-r0 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream zookeeper-3.8-advanced-compat package and not the zookeeper-3.8-advanced-compat package as distributed by Minimos.
See How to fix? for Minimos:latest relevant fixed versions and status.
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.
References
- https://www.cve.org/CVERecord?id=CVE-2026-84439
- https://github.com/advisories/GHSA-mxvw-9w3g-hmrq
- https://osv.dev/vulnerability/MINI-p9rc-6q36-vh92
- https://osv.dev/vulnerability/CVE-2026-84439
- https://lists.apache.org/thread/b7qnjvqjh393l0j07tmnb5ggg40sx3m6
- http://www.openwall.com/lists/oss-security/2026/09/15/6