Hostname Verification Flaw in Apache ZooKeeper Quorum TLS
CVE-2026-59969

7.5HIGH

Key Information:

Vendor

Apache
Status
Apache Zookeeper
Vendor
CVE Published:
16 September 2026

What is CVE-2026-59969?

A vulnerability in Apache ZooKeeper's quorum TLS configuration allows for insufficient hostname verification in FIPS-mode deployments. When specific settings related to SSL are enabled, a peer’s CA-trusted certificate can bypass hostname validation, potentially allowing a malicious or improperly issued certificate to access quorum communications. This issue can lead to unauthorized participation in quorum traffic, which opens avenues for leader election manipulation and disruption in data replication processes.

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/qf9kwsgtgbgtvwls6f4128184...
vendor-advisory

CVSS V3.1

Score:
7.5
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Erichen <chenyoulong20g@ict.ac.cn>
.