CVE-2026-59969
Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments.
Technology
Apache ZooKeeper
CVSS Score
7.5 / 10.0
Affected Versions
>=3.8.0 <3.8.7; >=3.9.0 <3.9.6
Upstream Fix
See upstream advisory
Published
September 16, 2026
OSSeva Coverage
Fixed upstream
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.
Is your Apache ZooKeeper deployment affected?
If you're running >=3.8.0 <3.8.7; >=3.9.0 <3.9.6, you need this patch. Book a discovery call to get covered.