Actively exploitedKnown ransomware use

CVE-2022-37042 Synacor Zimbra Collaboration Suite (ZCS) Authentication Bypass Vulnerability

Synacor Zimbra Collaboration Suite (ZCS) contains an authentication bypass vulnerability in MailboxImportServlet. This vulnerability was chained with CVE-2022-27925 which allows for unauthenticated remote code execution.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment

CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 11 Aug 2022.
CISA lists it as known to be used in ransomware campaigns.
Rated Critical severity (CVSS 9.8, scored by CISA).
This product type is often exposed to the internet, which is where attackers scan for it first.
It has been in the catalogue for 1,548 days. Systems still unpatched now have almost certainly been scanned for it.

The Vulnerability

What It Is

Zimbra Collaboration Suite (ZCS) 8.8.15 and 9.0 has mboximport functionality that receives a ZIP archive and extracts files from it. By bypassing authentication (i.e., not having an authtoken), an attacker can upload arbitrary files to the system, leading to directory traversal and remote code execution. NOTE: this issue exists because of an incomplete fix for CVE-2022-27925.

From Watch to Action

What To Do Now

1
Find it
Search your asset inventory and external attack surface for Synacor Zimbra Collaboration Suite (ZCS). Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management
2
Fix it
Apply updates per vendor instructions.
Vulnerability Management
3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response
4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 1 Sep 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Synacor Flaws

All 19 exploited Synacor vulnerabilities

Not Sure If You Are Exposed?

Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2022-37042 and every other exploited flaw on the list.

Check My Exposure

Evidence

PREVENTION

DETECTION & MITIGATION

GRC

INCIDENT RESPONSE

CLOUD SECURITY

CRITICAL INFRASTRUCTURE

REGULATED SERVICES

PUBLIC SERVICES

COMMERCIAL

THREAT INTELLIGENCE

MANAGED SECURITY

NETWORK & CLOUD

RISK & COMPLIANCE

DATA & APPLICATIONS

PEOPLE & EMAIL

FOR VENDORS

CVE-2022-37042 Synacor Zimbra Collaboration Suite (ZCS) Authentication Bypass Vulnerability

Should You Worry?

What It Is

What To Do Now

Find it

Fix it

Hunt for compromise

Prove it is fixed

Vendor Advisories

The Compliance Clock

More Exploited Synacor Flaws

Not Sure If You Are Exposed?

Sources