Description

Apache ZooKeeper, a widely used coordination service for distributed systems that manages configuration data, naming services, and synchronization, has recently received security updates to address two important vulnerabilities. The Apache Software Foundation released patches for issues that could potentially expose sensitive information and allow server impersonation in certain environments. The first vulnerability, identified as CVE-2026-24308, is related to improper handling of configuration data within the ZKConfig component. Because of this flaw, sensitive configuration values may be written in plain text to client log files when logging is enabled at the INFO level. Since INFO-level logging is often enabled by default in many production deployments, confidential details such as credentials or system parameters could unintentionally appear in logs. Anyone with access to these log files could potentially obtain sensitive information. This vulnerability was discovered and reported by security researcher Youlong Chen. The second vulnerability, tracked as CVE-2026-24281, involves a hostname verification bypass in the ZKTrustManager component. When validation of the IP Subject Alternative Name in a certificate fails, the system falls back to performing a reverse DNS lookup using PTR records. Attackers who are able to manipulate or spoof these PTR records may exploit this behavior to impersonate legitimate ZooKeeper servers or clients. For a successful attack, the adversary must also present a certificate trusted by the ZKTrustManager. Although this requirement increases the complexity of exploitation, the vulnerability still presents a risk in targeted environments. The issue was reported by Nikita Markevich and is internally tracked as ZOOKEEPER-4986. Both vulnerabilities affect ZooKeeper versions 3.8.0 through 3.8.5 and 3.9.0 through 3.9.4. Administrators are strongly encouraged to upgrade ZooKeeper deployments to versions 3.8.6 or 3.9.5, which address these issues. The updates prevent sensitive configuration data from being logged and introduce an option to disable reverse DNS lookups in client and quorum protocols. Security teams should also review older logs for potential credential exposure and rotate any affected authentication keys or passwords to maintain system security.