Assessment
Why it matters
CISA lists this vulnerability as known to be exploited; exploitation is confirmed; EPSS is 30.9%; technical severity is CVSS 6.1.
An issue was discovered in the Calendar feature in Zimbra Collaboration Suite 8.8.x before 8.8.15 patch 30 (update 1), as exploited in the wild starting in December 2021. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.
Who should care
- Teams operating Zimbra Collaborate Suite (ZCS), Zimbra Collaboration Suite
- Vulnerability and exposure management teams
- Security operations teams monitoring exploitation activity
Response plan
What I would do
- Confirm whether Zimbra Collaborate Suite (ZCS), Zimbra Collaboration Suite is present in the environment.
- Identify affected versions and establish whether vulnerable services are exposed or reachable.
- Vendor advisory from wiki.zimbra.com
- Review relevant security telemetry for evidence of attempted or successful exploitation.
- Document the remediation decision and track it to verified completion.
Treatment intelligence
Remediation intelligence
Vendor sources are listed before government and third-party guidance. Confirm product applicability and change prerequisites before deployment.
Verification noteAutomated link verification has not completed for this guidance yet.
Technical details
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CWE
- CWE-79
- Affected versions
- Synacor Zimbra Collaborate Suite (ZCS); Synacor Zimbra Collaboration Suite (Start Including 8.8.0, End Excluding 8.8.15 | Version 8.8.15 | Version 8.8.15 | Version 8.8.15)
- Fixed versions
- Synacor Zimbra Collaboration Suite (Fixed from 8.8.15)
- Published
- 9 February 2022
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
Signal timeline
- CVE published
- Added to CISA KEV
- Latest EPSS score: 30.9%
- Signal calculated at 75