# CVE-2026-84439: zookeeper: When audit logging is enabled (zookeeper.audit.enable=true), an unauthenticated attacker can inject arbitrary fields...

CVE-2026-84439 is fixed in zookeeper on 1 platform by DEBIAN-CVE-2026-84439 (version 3.9.6-1), released September 26, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-84439
- Priority: Routine
- CVSS: 5.3 (medium)
- EPSS: 0.0074
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 16, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | zookeeper Debian 14 | 3.9.6-1 | [DEBIAN-CVE-2026-84439](https://patchblox.com/security/data/fix/linux/debian-cve-2026-84439.md) | Sep 26, 2026 |

---

Data as of 2026-11-09T19:38:12Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data

Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.