What’s Vulnerable › Vulnerabilities

CVE-2026-24281: Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager

• Severity: high (CVSS 7.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-07 · updated 2026-07-15
• Weakness: CWE-295

Description

Hostname verification in Apache ZooKeeper ZKTrustManager falls back to reverse DNS (PTR) when IP SAN validation fails, allowing attackers who control or spoof PTR records to impersonate ZooKeeper servers or clients with a valid certificate for the PTR name. It's important to note that attacker must present a certificate which is trusted by ZKTrustManager which makes the attack vector harder to exploit. Users are recommended to upgrade to version 3.8.6 or 3.9.5, which fixes this issue by introducing a new configuration option to disable reverse DNS lookup in client and quorum protocols.

Affected products

• Apache Software Foundation Apache ZooKeeper: from 3.8.0 before 3.8.6; from 3.9.0 before 3.9.5 — fixed in 3.8.6, 3.9.5

How to fix

Upgrade to a fixed version: Apache Software Foundation Apache ZooKeeper 3.8.6, 3.9.5. Check the vendor advisory for mitigations.

References

• https://lists.apache.org/thread/088ddsbrzhd5lxzbqf5n24yg0mwh9jt2
• http://www.openwall.com/lists/oss-security/2026/03/07/4
• https://access.redhat.com/errata/RHSA-2026:10184
• https://access.redhat.com/errata/RHSA-2026:14272
• https://access.redhat.com/errata/RHSA-2026:14276
• https://access.redhat.com/errata/RHSA-2026:34608
• https://access.redhat.com/errata/RHSA-2026:8509
• https://access.redhat.com/security/cve/CVE-2026-24281
• https://bugzilla.redhat.com/show_bug.cgi?id=2445449
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-24281.json

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