CVE-2026-24281 Apache ZooKeeper: Reverse-DNS fallback enables hostname verification bypass in ZooKeeper ZKTrustManager
Attackers can bypass hostname verification in Apache ZooKeeper by spoofing reverse DNS records, potentially impersonating servers or clients.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-24281?
CVE-2026-24281 is a medium-severity vulnerability in Apache ZooKeeper, published on 7 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-24281?
5 open source packages ship an affected version, including org.apache.zookeeper:zookeeper and zookeeper. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.apache.zookeeper:zookeeper Maven | From 3.8.0 | 3.8.6 |
org.apache.zookeeper:zookeeper Maven | From 3.8.0 | 3.8.6 |
org.apache.zookeeper:zookeeper Maven | From 3.9.0 | 3.9.5 |
org.apache.zookeeper:zookeeper Maven | From 3.9.0 | 3.9.5 |
zookeeper Bitnami | From 3.8.0 | 3.8.6, 3.9.5 |
Products include Apache Zookeeper.
How do I fix CVE-2026-24281?
Upgrade org.apache.zookeeper:zookeeper to a fixed version for your release line: 3.8.6 or 3.9.5.
Is CVE-2026-24281 being exploited?
There is no known exploitation of CVE-2026-24281 in the wild and no public exploit code.
Other vulnerabilities in Apache ZooKeeper
- CVE-2024-51504 Apache ZooKeeper: Authentication bypass with IP-based authentication in Admin Server
- CVE-2023-44981 Apache ZooKeeper: Authorization bypass in SASL Quorum Peer Authentication
- CVE-2016-5017 Memory corruption in n/a
- CVE-2026-59739 Apache ZooKeeper: Information disclosure via SetWatches reconnect replay
- CVE-2026-59969 Apache ZooKeeper: Improper validation of certificate with host mismatch in FIPS mode
Sources
Also known as BIT-zookeeper-2026-24281, CLEANSTART-2026-AS23649, CLEANSTART-2026-UU38488, DEBIAN-CVE-2026-24281, ECHO-6fcc-5bac-4e91, GHSA-7xrh-hqfc-g7qr and 21 more.