CVE-2026-59739 Apache ZooKeeper: Information disclosure via SetWatches reconnect replay
Attackers can discover restricted ZooKeeper paths by exploiting a missing ACL check during reconnect replay, potentially exposing sensitive path names.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59739?
CVE-2026-59739 is a high-severity vulnerability in Apache ZooKeeper, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Information disclosure via SetWatches reconnect replay in Apache ZooKeeper due to missing ACL check. An attacker can discover ACL-restricted paths by registering exists-watches on non-existent paths, then reconnecting after the paths are created with restricted ACLs. Issue is caused by incomplete fix for CVE-2024-23944 (ZOOKEEPER-4799). The fix added ACL checking to WatchManager.triggerWatch(). However, DataTree.setWatches() — the SetWatches/SetWatches2 reconnect replay handler — still calls watcher.process(event) with null ACL, bypassing the check entirely. It's important to note that only the path is exposed by this vulnerability, not the data of znode, but since znode path can contain sensitive information like user name or login ID, this issue is potentially critical.
Users are recommended to upgrade to version 3.9.6, 3.8.7 which fixes the issue.
Weakness: CWE-862
Which versions are affected by CVE-2026-59739?
1 open source package ship an affected version, including zookeeper. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
zookeeper Bitnami | From 3.8.0 | 3.8.7, 3.9.6 |
Products include Apache Zookeeper.
How do I fix CVE-2026-59739?
Upgrade zookeeper to a fixed version for your release line: 3.8.7 or 3.9.6.
Is CVE-2026-59739 being exploited?
There is no known exploitation of CVE-2026-59739 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-2026-59969 Apache ZooKeeper: Improper validation of certificate with host mismatch in FIPS mode
- CVE-2026-79993 Missing authorization in Apache ZooKeeper
Sources
Also known as BIT-zookeeper-2026-59739, CLEANSTART-2026-JM28284, CLEANSTART-2026-ML04549, CLEANSTART-2026-PX58451, CLEANSTART-2026-YK34202, DEBIAN-CVE-2026-59739 and 4 more.