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

Published Mar 7, 2026
·
Updated

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

7 affected componentsFixes available
Apache Zookeeper<3.8.6, <3.9.5
maven/org.apache.zookeeper:zookeeper>=3.9.0<3.9.5
3.9.5
maven/org.apache.zookeeper:zookeeper>=3.8.0<3.8.6
3.8.6
Apache Zookeeper>=3.8.0<3.8.6
Apache Zookeeper>=3.9.0<3.9.5
IBM Engineering Requirements Management DOORS and DOORS Web Access<=9.7.2.1 - 9.7.2.11
IBM Engineering Requirements Management DOORS and DOORS Web Access<=9.6.1.1 - 9.6.1.13

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade maven/org.apache.zookeeper:zookeeper to a version that resolves this vulnerability.

    Fixed in 3.9.5
  2. Upgrade

    Upgrade maven/org.apache.zookeeper:zookeeper to a version that resolves this vulnerability.

    Fixed in 3.8.6
  3. Upgrade

    Upgrade Apache ZooKeeper to a version that resolves this vulnerability.

    Fixed in 3.8.6
  4. Upgrade

    Upgrade Apache ZooKeeper to a version that resolves this vulnerability.

    Fixed in 3.9.5

Event History

Mar 7, 2026
CVE Published
via MITRE·08:50 AM
Data Sourced
via MITRE·08:50 AM
DescriptionWeakness
Data Sourced
via Red Hat·09:01 AM
DescriptionSeverityAffected Software
Data Sourced
via NVD·09:16 AM
DescriptionSeverityWeaknessAffected Software
Advisory Published
via GitHub·09:30 AM
Data Sourced
via GitHub·09:30 AM
DescriptionSeverityWeaknessAffected Software
Jul 6, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

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Frequently Asked Questions

1

What is the severity of CVE-2026-24281?

CVE-2026-24281 has been rated as a high severity vulnerability due to its potential to allow attackers to impersonate ZooKeeper instances.

2

How do I fix CVE-2026-24281?

To mitigate CVE-2026-24281, it is recommended to upgrade Apache ZooKeeper to version 3.9.6 or later where this vulnerability has been addressed.

3

What systems are affected by CVE-2026-24281?

CVE-2026-24281 affects Apache ZooKeeper versions prior to 3.9.6, including all versions up to 3.9.5.

4

What are the consequences of exploiting CVE-2026-24281?

Exploiting CVE-2026-24281 allows attackers to bypass hostname verification and potentially impersonate ZooKeeper servers, leading to unauthorized access.

5

Is there a workaround for CVE-2026-24281 until a fix is available?

Currently, there are no recommended workarounds for CVE-2026-24281; the best approach is to upgrade to a patched version of Apache ZooKeeper.

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