zookeeper: Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments
CVE-2026-59969 is fixed in zookeeper on 1 platform by DEBIAN-CVE-2026-59969 (version 3.9.6-1), released September 26, 2026. It is not reported as exploited. Patch Radar priority: High.
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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| zookeeper · Debian 14 | 3.9.6-1 | DEBIAN-CVE-2026-59969 | Sep 26, 2026 |
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