CVE-2026-93640: Zimbra Collaboration Suite Local Privilege Escalation via Unrestricted zmunbound Sudo Configuration
A local privilege escalation vulnerability in the optional dnscache package of Zimbra Collaboration Suite (ZCS) allows the Unix zimbra account to access files with root privileges. The passwordless sudo policy permits arbitrary arguments to zmunbound, whose wrapper forwards them to Unbound without restricting the configuration path. An attacker can supply a configuration that retains root privileges and disables the chroot. Include directives expose root-readable file contents through parser errors, while an attacker-selected logfile path creates a root-owned file or appends Unbound log records to an existing file. This can disclose password hashes and private keys and corrupt privileged configuration files, preventing affected services from starting with the modified configuration. The affected configuration is present in ZCS 10.1.16 and 10.1.21 dnscache packages.
Affected Software
Event History
Frequently Asked Questions
Who can exploit this issue?
An attacker needs local access to the Unix zimbra account, or the ability to execute commands as that account. The issue is in the optional dnscache package's passwordless sudo configuration.
Are default ZCS installations affected?
Only installations with the affected dnscache package configuration are described as vulnerable. The affected configuration is present in ZCS 10.1.16 and 10.1.21 dnscache packages.
What could an attacker do after exploiting it?
They can read root-readable file contents through Unbound parser errors, including password hashes and private keys. They can also create root-owned files or append log data to existing privileged files, potentially corrupting configuration and stopping affected services from starting.
What configuration behavior enables the escalation?
The zmunbound sudo policy allows arbitrary arguments without a password, and its wrapper passes them to Unbound without restricting the configuration path. An attacker can provide a configuration that disables the chroot and retains root privileges.