CVE-2024-27443
Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 9 June 2025). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- CVSS 3.1
- 6.1 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 24.61% probability · 98th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 19 May 2025 · due 9 June 2025
- Weakness
- CWE-79
- Affected
- zimbra/collaboration
- Source
- cve@mitre.org
EPSS 24.6% since 30 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P46#Security_Fixes ; https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes ; https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes ; https://nvd.nist.gov/vuln/detail/CVE-2024-27443
References
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_FixesRelease Notes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_FixesRelease Notes
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443US Government Resource
- https://www.welivesecurity.com/en/eset-research/operation-roundpress/Press/Media Coverage
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.