CVE-2026-59969: CWE-297 Improper Validation of Certificate with Host Mismatch in Apache Software Foundation 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.
AI Analysis
Technical Summary
CVE-2026-59969 describes an improper validation of certificates (CWE-297) in Apache ZooKeeper quorum TLS when operating in FIPS mode with specific SSL quorum and hostname verification settings enabled. The Java SSLSocket quorum path accepts peer certificates trusted by a CA even if the Subject Alternative Name (SAN) does not match the hostname of the connected peer. This flaw allows a malicious or misissued peer certificate to join the quorum, participate in leader election, and access replication traffic, potentially undermining the integrity of the ZooKeeper ensemble. The vulnerability affects Apache ZooKeeper versions from 3.8.0 up to 3.8.6 and from 3.9.0 up to 3.9.5. The issue is resolved in versions 3.8.7 and 3.9.6.
Potential Impact
An attacker with a malicious or misissued CA-trusted certificate can impersonate a quorum peer by bypassing hostname verification in TLS connections. This enables the attacker to join the ZooKeeper quorum, participate in leader election, and access replication traffic, potentially compromising the integrity and trustworthiness of the distributed coordination service.
Mitigation Recommendations
Users should upgrade Apache ZooKeeper to versions 3.8.7 or 3.9.6, which contain the official fix for this vulnerability. No other mitigations are indicated by the vendor advisory.
CVE-2026-59969: CWE-297 Improper Validation of Certificate with Host Mismatch in Apache Software Foundation Apache ZooKeeper
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.
Affected software
Apache Software Foundation
Apache ZooKeeper
pkg:maven/Apache Software Foundation/org.apache.zookeeper:zookeeperRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-59969 describes an improper validation of certificates (CWE-297) in Apache ZooKeeper quorum TLS when operating in FIPS mode with specific SSL quorum and hostname verification settings enabled. The Java SSLSocket quorum path accepts peer certificates trusted by a CA even if the Subject Alternative Name (SAN) does not match the hostname of the connected peer. This flaw allows a malicious or misissued peer certificate to join the quorum, participate in leader election, and access replication traffic, potentially undermining the integrity of the ZooKeeper ensemble. The vulnerability affects Apache ZooKeeper versions from 3.8.0 up to 3.8.6 and from 3.9.0 up to 3.9.5. The issue is resolved in versions 3.8.7 and 3.9.6.
Potential Impact
An attacker with a malicious or misissued CA-trusted certificate can impersonate a quorum peer by bypassing hostname verification in TLS connections. This enables the attacker to join the ZooKeeper quorum, participate in leader election, and access replication traffic, potentially compromising the integrity and trustworthiness of the distributed coordination service.
Mitigation Recommendations
Users should upgrade Apache ZooKeeper to versions 3.8.7 or 3.9.6, which contain the official fix for this vulnerability. No other mitigations are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- apache
- Date Reserved
- 2026-07-07T18:50:40.959Z
- State
- PUBLISHED
Threat ID: 6aaa659d55bf5e2cf5501bea
Added to database: 09/16/2026, 09:47:09 UTC
Last enriched: 09/16/2026, 10:01:45 UTC
Last updated: 09/16/2026, 10:32:24 UTC
Views: 4
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