CVE-2024-27443: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

CISA Known Exploited Vulnerabilities

Name

Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability

Vendor

Synacor

Product

Zimbra Collaboration Suite (ZCS)

Added to the catalog

2025-05-19

Due date for US federal agencies

2025-06-09

Weaknesses

CWE-79

Catalog version

2026.10.30

Zimbra Collaboration contains a cross-site scripting (XSS) vulnerability in the CalendarInvite feature of the Zimbra webmail classic user interface. An attacker can exploit this vulnerability via an email message containing a crafted calendar header, leading to the execution of arbitrary JavaScript code.

Required action (CISA)

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• 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

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2024-08-12T15:15:20.283

Last modified

2026-06-17T07:19:54.627

Weaknesses

CWE-79

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.

References

• https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes (Release Notes)
• https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes (Release Notes)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443 (US Government Resource)
• https://www.welivesecurity.com/en/eset-research/operation-roundpress/ (Press/Media Coverage)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:42:15.686Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2024-27443

CVE record

Assigner

mitre

State

PUBLISHED

Published

2024-08-12T00:00:00.000Z

Updated

2025-10-21T22:55:48.688Z

Problem types

n/a

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.

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

Read on 2026-11-03T02:06:08.570Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2024/27xxx/CVE-2024-27443.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/