What is CVE-2024-27443?
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.
The record classifies CVE-2024-27443 under weakness class CWE-79. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 38 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 809 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 6.1 — MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - EPSS (FIRST)
- 23.6% probability of exploitation in the next 30 days, higher than 97.7% of all scored CVEs
- CISA KEV
- Listed since 2025-05-19, federal remediation deadline 2025-06-09
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2024-08-12, last modified 2025-10-21
Is CVE-2024-27443 being exploited?
CISA added CVE-2024-27443 to the Known Exploited Vulnerabilities catalog on 2025-05-19, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2025-06-09 under BOD 22-01. Weaponised exploit code for CVE-2024-27443 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2024/CVE-2024-27443.yaml). It currently carries a trending score of 49 in the Threadlinqs vulnerability feed.
- trickest/cve (trickest)
Affected products and versions
- Zimbra: Collaboration, Collaboration 9.0.0
Showing 2 of 38 recorded product entries.
How to fix CVE-2024-27443
Because CVE-2024-27443 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2025-06-09. No vendor patch reference has been recorded for CVE-2024-27443 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2024-27443
2 tracked threats in the Threadlinqs corpus reference CVE-2024-27443, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on .