Threat Intelligence / CVE / CVE-2024-27443

CVE-2024-27443 — Zimbra Collaboration

CISA KEV
CVSS v3.1 6.1 (MEDIUM) · EPSS 32.4% (higher than 96.8% of all scored CVEs) · Priority 9/10 · Published 2024-08-12

As of 2025-10-31, CVE-2024-27443 is a MEDIUM-severity vulnerability in Zimbra Collaboration, CVSS v3.1 6.1, EPSS 32.4% (96.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2025-05-19), with a US federal remediation deadline of 2025-06-09. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2024-27443, most recently “APT28/UAC-0001 Sustained Cyber Espionage Against Ukraine & EU (2024-2026 New TTPs)”.

Last updated: 2025-10-31

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 762 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)
32.4% probability of exploitation in the next 30 days, higher than 96.8% 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 2025-10-31

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. It currently carries a trending score of 39 in the Threadlinqs vulnerability feed.

Affected products and versions

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

1 tracked threat in the Threadlinqs corpus references CVE-2024-27443, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Seeded from nvd and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2024-27443 are available via the Threadlinqs MCP server (Purple tier). View plans →

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