Log Injection Vulnerability in Apache ZooKeeper Affects Multiple Versions
CVE-2026-84439

5.3MEDIUM

Key Information:

Vendor

Apache
Status
Apache Zookeeper
Vendor
CVE Published:
16 September 2026

What is CVE-2026-84439?

A log injection vulnerability in Apache ZooKeeper allows unauthenticated attackers to manipulate audit logs by injecting arbitrary fields through crafted digest authentication requests. This allows attackers to spoof audit results, forge operation types, and corrupt forensic evidence. When audit logging is enabled, attackers may exploit tab characters in usernames to alter the output of zookeeper_audit.log, making it appear as though legitimate operations occurred. This can severely undermine the integrity of audit parsing and incident response mechanisms. Users are advised to upgrade to versions 3.9.6 or 3.8.7 to mitigate this issue.

Affected Version(s)

Apache ZooKeeper 3.9.0 <= 3.9.5

Apache ZooKeeper 3.8.0 <= 3.8.6

References

https://lists.apache.org/thread/b7qnjvqjh393l0j07tmnb5ggg...
vendor-advisory

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Youlong Chen Institute of Computing Technology <chenyoulong20g@ict.ac.cn>
.