CVE-2026-59969

high

Apache ZooKeeper quorum TLS fails to enforce peer hostname verification in FIPS-mode deployments.

Vendor / product: Apache — zookeeper

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.

CVSS

7.5

7.5 (CVSS v3.1)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Severity source: NVD CVSS v3.1 (134c704f-9b21-4f2e-91b3-4a467353bcc0)

Timeline (UTC)

Published: 2026-09-16 10:16

Modified: 2026-09-18 14:31

NVD status: Analyzed

Last synced 1 day ago

Verified against the source API 2026-10-27 06:54 UTC

Exploitation

Not listed in CISA KEV (as of last catalog sync)

Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

apache / zookeeper ≥3.8.0 <3.8.7, ≥3.9.0 <3.9.6

Weakness classification (CWE)

CWE-297

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

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

References

https://lists.apache.org/thread/qf9kwsgtgbgtvwls6f41281846xg0rss security@apache.org
http://www.openwall.com/lists/oss-security/2026/09/15/4 af854a3a-2127-422b-91ae-364da2661108

Data sources

NVD CVE API 2.0 — fetched 2026-10-27 06:54 UTC · record ↗

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CVE-2026-59969

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