What it is
CVE-2024-27443 is an unauthenticated vulnerability affecting Zimbra Zimbra Collaboration (ZCS). An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in...
Vulnerability report
Exploited in the wild
Confirmed confidence
In CISA KEV
CVE-2024-27443
Zimbra Collaboration (ZCS) Cross-Site Scripting
Zimbra / Zimbra Collaboration (ZCS)
- Severity
- CVSS 6.1 · Medium
- Confidence
- Confirmed
- Exploit status
- Exploited in the wild
- EPSS
- 23.6%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is confirmed.
Who is affected?
Zimbra / Zimbra Collaboration (ZCS).
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the CalendarInvite feature of the Zimbra webmail classic user interface, because of improper input validation in the handling of the calendar header.
An attacker can exploit this via an email message containing a crafted calendar header with an embedded XSS payload. When a victim views this message in the Zimbra webmail classic interface, the payload is executed in the context of the victim's session, potentially leading to execution of arbitrary JavaScript code.
- Published
- 12 Aug 2024
- Exploitation Reported
- 21 May 2025
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
Tags
cisa
nuclei_scanner
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2024-27443
- wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7 wiki.zimbra.com · CVE Record https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes
- wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39 wiki.zimbra.com · CVE Record https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
CVE
Independent exploitation attestation added to the KEV Intelligence record.
Proof of concept available
Nuclei Templates
Public scanner or PoC coverage increases practical exploitability.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| CVE First | 2025-05-21 13:10 UTC |
| CISA | 2026-06-02 14:07 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
Nuclei template detected 01 Jun 2026.
View Nuclei template (opens in new tab)Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →Scanner Artifacts
Scanner and exploit-framework references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2024/CVE-2024-27443.yaml | 01 Jun 2026 |
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
6.1
Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS
23.6%
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
Zimbra Collaboration - Cross-Site Scripting (XSS)
nuclei · Created Unknown
Timeline
From disclosure to observed exploitation
-
Public PoC available
Public proof-of-concept code published
-
Added to CISA KEV
Listed in the CISA Known Exploited Vulnerabilities catalog
-
Nuclei template available
Scanner coverage available
-
Added to KEV Intelligence KEV Feed
High-confidence, third-party attested exploitation
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2024-27443
Free JSON includes basic KEV fields{
"cve_id": "CVE-2024-27443",
"confidence": "Confirmed",
"cvss_score": 6.1,
"cvss_estimated": false,
"epss_score": 0.23632,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.