Vulnerability · Published Mar 7, 2026 · Assigned by apache

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

Medium 5.9

In plain English

A medium-severity improper certificate validation in Apache ZooKeeper from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.7%top 46.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	zookeeper	no fix listed	DEBIAN-CVE-2026-24281
Debian:13	zookeeper	no fix listed	DEBIAN-CVE-2026-24281
Debian:14	zookeeper	3.9.5-1	DEBIAN-CVE-2026-24281
Maven	org.apache.zookeeper:zookeeper	3.8.6	GHSA-7xrh-hqfc-g7qr
Maven	org.apache.zookeeper:zookeeper	3.9.5	GHSA-7xrh-hqfc-g7qr
Ubuntu:22.04:LTS	zookeeper	no fix listed	UBUNTU-CVE-2026-24281
Ubuntu:24.04:LTS	zookeeper	no fix listed	UBUNTU-CVE-2026-24281
Ubuntu:25.10	zookeeper	no fix listed	UBUNTU-CVE-2026-24281
Ubuntu:26.04:LTS	zookeeper	no fix listed	UBUNTU-CVE-2026-24281
Ubuntu:26.10	zookeeper	no fix listed	UBUNTU-CVE-2026-24281

Affected products (as reported)

Vendor	Product	Versions
Apache Software Foundation	Apache ZooKeeper	3.9.0 – through 3.9.43.8.0 – through 3.8.5

Weakness: CWE-350, CWE-295 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

References

https://lists.apache.org/thread/088ddsbrzhd5lxzbqf5n24yg0mwh9jt2 vendor-advisory
http://www.openwall.com/lists/oss-security/2026/03/07/4
https://access.redhat.com/security/cve/CVE-2026-24281 vdb-entry, x_refsource_REDHAT
RHBZ#2445449 issue-tracking, x_refsource_REDHAT
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-24281.json x_sadp-csaf-vex
https://access.redhat.com/errata/RHSA-2026:14276 vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:14272 vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:8509 vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:10184 vendor-advisory, x_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:34608 vendor-advisory, x_refsource_REDHAT