CVE-2026-50056: Zimbra Collaboration Suite Local Privilege Escalation via zmmailboxdmgr JVM Argument Injection
A local privilege escalation vulnerability in the zmmailboxdmgr launcher of Zimbra Collaboration Suite (ZCS) allows the Unix zimbra account to execute arbitrary commands as root. The passwordless sudo interface accepts JVM arguments that are not adequately restricted. An attacker can postpone Jetty's privilege drop, register an OnOutOfMemoryError command and force heap exhaustion during startup, causing the command to execute while the JVM still runs as root. Exploitation requires local command execution as zimbra on a mailbox server and interrupts mailboxd during the malicious restart. ZCS 10.1.16 and 10.1.21 are affected.
Affected Software
Event History
Frequently Asked Questions
Who is exposed to this vulnerability?
Mailbox servers running Zimbra Collaboration Suite 10.1.16 or 10.1.21 are affected. Exploitation requires local command execution as the Unix zimbra account on the mailbox server.
What access does an attacker need to exploit it?
The attacker must already be able to run commands locally as zimbra. They can then use the passwordless sudo interface for zmmailboxdmgr to supply insufficiently restricted JVM arguments and execute commands as root.
Does exploitation affect service availability?
Yes. The attack forces heap exhaustion during a malicious mailboxd restart, which interrupts mailboxd while the exploit is performed.