CVE-2026-59969 — Apache ZooKeeper: Improper validation of certificate with host mismatch in FIPS mode

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
Apache Software Foundation / Apache ZooKeeper	affected 3.9.0 through 3.9.5; affected 3.8.0 through 3.8.6

CWE

CWE-297

References

https://lists.apache.org/thread/qf9kwsgtgbgtvwls6f41281846xg0rss

ADP enrichment

CVE

No English description supplied.

http://www.openwall.com/lists/oss-security/2026/09/15/4

CISA-ADP

No English description supplied.

No references supplied.