CVE-2026-59739

Two four-letter commands 'wchp/wchc' are CPU intensive and can cause a spike in CPU utilization on the Apache ZooKeeper server if abused, leading to the server being unable to serve legitimate client requests.

Buffer overflow in the C cli shell in Apache Zookeeper before version 3.4.9 and 3.5.x before version 3.5.3, occurring when using the 'cmd:' batch mode syntax, allows attackers to have unspecified impact via a long command string.

An unauthenticated attacker can inject arbitrary fake log lines into Apache ZooKeeper's operational log by sending a crafted add_auth("ensemble", ...) request containing newline characters. The ensemble name is not sanitized before being logged, allowing the attacker to forge log entries indistinguishable from genuine ones.

When audit logging is enabled, an unauthenticated attacker can inject arbitrary fields into Apache ZooKeeper's audit log by sending a digest authentication request with tab characters in the username. The injected tabs are parsed as field separators, allowing the attacker to spoof audit results and operations.

In Apache ZooKeeper, the deleteContainer opcode (0x14/20) is processed without verifying ACL permissions, allowing any authenticated client to delete empty persistent, container, and TTL nodes even without proper permissions. This is an authorization bypass and ACL enforcement bug.

In Apache ZooKeeper, in FIPS mode, peer hostname verification in quorum TLS is not enforced. Despite enabling the relevant options, the connection accepts a CA-trusted certificate even if the SAN does not match the connected host, allowing a malicious certificate to join quorum traffic.

In Apache ZooKeeper versions 3.8.5 and 3.9.4, improper handling of configuration values in ZKConfig allows an attacker to expose sensitive information stored in client configuration in the client's logfile. Configuration values are exposed at INFO level logging, potentially affecting production systems.

In Apache ZooKeeper, hostname verification in 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. The attacker must present a certificate trusted by ZKTrustManager, making the attack vector harder to exploit.