Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | org.apache.zookeeper:zookeeper | >= 3.8.0, < 3.8.6, >= 3.9.0, < 3.9.5 | 3.8.6, 3.9.5 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-24281
- https://github.com/apache/zookeeper/commit/66c4efecdda1302d9cfb3af9eedb122b74452bf3
- https://github.com/apache/zookeeper
- https://issues.apache.org/jira/browse/ZOOKEEPER-4986
- https://lists.apache.org/thread/088ddsbrzhd5lxzbqf5n24yg0mwh9jt2
- http://www.openwall.com/lists/oss-security/2026/03/07/4
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
CWE-295, CWE-297- Platform
- Java / Kotlin (Maven)
- Package
org.apache.zookeeper:zookeeper- Disclosed
- 07.03.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-7xrh-hqfc-g7qr - CC BY 4.0
Vulnerability history: org.apache.zookeeper:zookeeper
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 9
- First → latest
- 05.2019 03.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 5
- Medium 3
Disclosures per year
- 2019: 1
- 2020: 0
- 2021: 0
- 2022: 2
- 2023: 1
- 2024: 2
- 2025: 1
- 2026: 2
-
Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager this entry
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