CVE-2024-45519

CVE-2024-45519 is an access-control weakness (CWE-284) in the postjournal service of Synacor Zimbra Collaboration Suite (ZCS) that allows an unauthenticated remote attacker to execute operating-system commands on the mail server. The postjournal service handles Zimbra's email journaling, and the flaw is reached by sending crafted mail/SMTP traffic to a vulnerable server, with no credentials or user interaction required. Successful exploitation gives the attacker command execution on the ZCS host, typically a foothold for stealing mailbox data and credentials, deploying webshells, or staging broader intrusion and ransomware activity. Any organization running ZCS is in scope, especially internet-exposed mail servers operated by enterprises, hosting/ISP providers, education, and government. Exploitation is confirmed in the wild: CISA added the flaw to the KEV catalog on 2024-10-03, and EPSS assigns a 99.9% probability of exploitation within 30 days (100th percentile), though no public PoC is known.

What to do: Upgrade ZCS to the latest patch release per Synacor's advisory for this CVE, prioritizing internet-facing mail servers, since CISA's KEV required action is to apply vendor mitigations or discontinue use of the product if mitigations are unavailable. If patching cannot be done immediately, restrict untrusted network access to the postjournal/SMTP path and treat the host as presumptively compromised because exploitation is already in the wild. Check postjournal logs and unexpected child processes or dropped files on the server for signs of compromise, and re-verify after patching.