What’s Vulnerable › Vulnerabilities
CVE-2026-59739: Apache ZooKeeper: Information disclosure via SetWatches reconnect replay
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.6% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-09-16 · updated 2026-09-18
- Weakness: CWE-862
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.
Affected products
- Apache Software Foundation Apache ZooKeeper: from 3.8.0 before 3.8.7; from 3.9.0 before 3.9.6 — fixed in 3.8.7, 3.9.6
How to fix
Upgrade to a fixed version: Apache Software Foundation Apache ZooKeeper 3.8.7, 3.9.6. Check the vendor advisory for mitigations.
References
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