Quick answers
- Is CVE-2026-59739 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-59739 being exploited in the wild.
- How severe is CVE-2026-59739?
- High severity, with a CVSS score of 7.5, published 16 September 2026.
- Which products and versions are affected?
- Apache Zookeeper prior to 3.8.7 and 3.9.6.
- Is there a fix for CVE-2026-59739?
- A patch was published on 2026-09-16: Patches available in versions 3.8.7 and 3.9.6 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-59739 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-59739?
- Check whether you run Apache Zookeeper at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a missing ACL (Access Control List) check in the SetWatches reconnect replay handler. It stems from an incomplete fix to CVE-2024-23944: while the fix added ACL validation to WatchManager.triggerWatch(), the vulnerable DataTree.setWatches() method still calls watcher.process(event) with null ACL context, bypassing the check entirely. An attacker can exploit this by registering exists-watches on non-existent paths, then reconnecting after those paths are created with restricted ACLs—the ZooKeeper server will replay the watch events without proper ACL validation, exposing the path names to the connecting client. The attack requires the ability to connect to ZooKeeper as a client; no data contents are leaked, only the path names. Patches are available in versions 3.9.6 and 3.8.7.
Affected products
- Apache ZooKeeper prior to 3.8.7 and 3.9.6
Timeline
- 2026-09-16: disclosed
- 2026-09-16: patched: Patches available in versions 3.8.7 and 3.9.6