CVE-2026-59969 Apache ZooKeeper: Improper validation of certificate with host mismatch in FIPS mode
Attackers can bypass hostname verification in FIPS mode to join quorum traffic and manipulate leader election or replication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59969?
CVE-2026-59969 is a high-severity vulnerability in Apache ZooKeeper, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments. When sslQuorum=true, zookeeper.fips-mode=true, ssl.quorum.hostnameVerification=true, and ssl.quorum.clientHostnameVerification=true are enabled, the Java SSLSocket quorum path accepts a CA-trusted peer certificate whose SAN does not match the connected host. A malicious or misissued peer certificate can therefore join quorum traffic, participate in leader election, and enter replication flows.
Users are recommended to upgrade to version 3.8.7 or 3.9.6, which fixes the issue.
Weakness: CWE-297
Which versions are affected by CVE-2026-59969?
1 open source package ship an affected version, including zookeeper. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
zookeeper Bitnami | From 3.8.0 | 3.8.7, 3.9.6 |
Products include Apache Zookeeper.
How do I fix CVE-2026-59969?
Upgrade zookeeper to a fixed version for your release line: 3.8.7 or 3.9.6.
Is CVE-2026-59969 being exploited?
There is no known exploitation of CVE-2026-59969 in the wild and no public exploit code.
Other vulnerabilities in Apache ZooKeeper
- CVE-2024-51504 Apache ZooKeeper: Authentication bypass with IP-based authentication in Admin Server
- CVE-2023-44981 Apache ZooKeeper: Authorization bypass in SASL Quorum Peer Authentication
- CVE-2016-5017 Memory corruption in n/a
- CVE-2026-59739 Apache ZooKeeper: Information disclosure via SetWatches reconnect replay
- CVE-2026-79993 Missing authorization in Apache ZooKeeper
Sources
Also known as BIT-zookeeper-2026-59969, CLEANSTART-2026-JQ32755, CLEANSTART-2026-NB78178, CLEANSTART-2026-QE83789, CLEANSTART-2026-XH38250, DEBIAN-CVE-2026-59969 and 4 more.