CVE-2022-27925: Synacor Zimbra Collaboration Suite (ZCS) Arbitrary File Upload Vulnerability

CVE-2022-27925 is an arbitrary file upload weakness in Synacor Zimbra Collaboration Suite (ZCS), specifically in the mboximport functionality. An authenticated attacker can abuse it to place files that enable remote code execution. Public reporting also notes it has been chained with CVE-2022-37042 to achieve unauthenticated remote code execution. The flaw matters because Zimbra often sits at the edge of email and collaboration infrastructure; successful abuse can give an attacker a foothold on the mail server, and this vulnerability has known ransomware use. Confirm all version, patch, and configuration details against the vendor advisory.

How it works

The reported weakness is tracked as CWE-22 (path traversal related). In this product, the issue sits in mboximport: an authenticated user can upload arbitrary files in a way that leads to remote code execution on the Zimbra host. Exact request paths, file locations, and payload mechanics are not detailed here and must be taken from the vendor advisory and reliable technical write-ups—do not assume specifics.

Separately, the vulnerability has been chained with CVE-2022-37042. That second issue removes the authentication barrier in the combined attack path, so defenders should treat the pair as enabling unauthenticated remote code execution when both are present and unpatched. Attackers who gain code execution on a collaboration suite can typically read mail, harvest credentials, move laterally, or deploy ransomware; the facts explicitly note known ransomware use for this CVE.

Am I affected? How to find it in your systems

Zimbra Collaboration Suite commonly runs as an on-premises or self-hosted mail and groupware platform (web UI, SMTP/IMAP, and related services), often exposed to the internet for remote access. Inventory every host that provides Zimbra services: check package names, install directories, and admin consoles for ZCS deployments. Compare installed builds to the fixed versions listed in the vendor advisory for CVE-2022-27925 (and related CVE-2022-37042); do not rely on version guesses from secondary sources.

• Enumerate Zimbra nodes via CMDB, vulnerability scanners, configuration management, and network service discovery (HTTP/S on typical Zimbra ports, mail-related listeners).
• Confirm whether mboximport or mailbox import features are enabled or reachable by authenticated users; lock down or document any exposure.
• Review authentication and access logs for unusual import or upload activity, unexpected file writes under Zimbra directories, new or modified web-accessible scripts, and outbound connections from the Zimbra host that do not match baseline mail traffic.
• If you use a WAF, IDS/IPS, or EDR, search for alerts tied to this CVE family or to anomalous authenticated file-upload patterns against Zimbra endpoints; validate hits against the vendor’s description rather than generic signatures alone.

Any system still on an unfixed release, or where the chained issue is also unpatched, should be treated as at risk until verified otherwise.

How to remediate

Patch first. Apply the updates Synacor provides for Zimbra Collaboration Suite exactly as described in the vendor advisory and in line with CISA’s required action: apply updates per vendor instructions. Schedule maintenance windows promptly for internet-facing and high-value mail hosts.

• After patching, verify the installed build matches the fixed release and re-test import/upload paths if your change-control process allows.
• Restrict who can authenticate to Zimbra admin and import functions; enforce strong authentication and least privilege for any account that can reach mboximport-related features.
• Harden the host: limit network exposure of management and import interfaces, keep the OS and dependencies current, and ensure web and application processes run with minimal privileges.
• Rotate credentials and review mail-store integrity if you have any indication the system was reachable while vulnerable.

If you can't patch immediately

Reduce exposure until the vendor update is installed. Compensating controls do not replace the patch but can lower likelihood and impact of exploitation, including ransomware follow-on activity.

• Segment Zimbra hosts from general user LANs and from critical internal systems; allow only necessary mail and admin flows.
• Block or restrict external access to mboximport and related administrative endpoints at the reverse proxy, load balancer, or firewall; prefer VPN or jump-host access for admins.
• If available, deploy virtual patching or WAF rules that target the vulnerable upload/import behavior described by the vendor—tune carefully to avoid breaking legitimate mail operations and confirm rule coverage against the advisory.
• Disable or tightly ACL the mailbox import functionality if business operations allow it until patched.
• Increase monitoring: alert on authenticated upload/import spikes, unexpected new files under Zimbra web or data directories, web shells or odd process trees spawned by Zimbra services, and unusual outbound traffic. Retain logs for incident response.

If your data may have been exposed

Actively exploited vulnerabilities—especially those with known ransomware use—often precede account takeover, mail theft, or full environment compromise. If this Zimbra instance was unpatched and reachable, assume possible exposure of mail data and credentials until you investigate. Isolate suspect hosts, preserve logs and disk evidence, reset privileged and user passwords as appropriate, and follow your incident-response plan. You can also run a free exposure scan of your email addresses against known breach datasets to see whether associated identities already appear in public breach collections, then prioritize monitoring and credential hygiene accordingly.