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.
do firstApply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Can a WAF block it? Yes. The malicious input is delivered via an email message viewed in the webmail interface, specifically in a calendar header that contains an embedded script payload. A WAF could partially detect this by matching unusual script content in calendar headers, but normal emails may also contain complex headers, so filtering is only partly reliable. A custom WAF rule can filter email message with a crafted calendar header containing script code, but attackers can vary the request. No tracked WAF vendor has published a rule for this CVE yet.
What a custom rule would match: email message with a crafted calendar header containing script code
Also consider: patch · custom WAF rule · CSP · output encoding
Based on an AI reading of the CVE description, and no vendor rule found yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Is CVE-2024-27443 being exploited?
Yes. CVE-2024-27443 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2024-27443?
CVE-2024-27443 is rated Medium with a CVSS score of 6.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2024-27443?
Yes. A fix has been recorded for CVE-2024-27443. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2024-27443 affect?
CVE-2024-27443 affects zimbra:collaboration. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
public exploits
Detection templates only, no public exploit found: 1 Nuclei template
- Zimbra Collaboration - Cross-Site Scripting (XSS) · detection template · medium
Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.
cisa ssvc
- exploitation
- active
- automatable
- no
- technical impact
- total
Assessed by CISA 21 May 2025 (SSVC 2.0.3).
timeline
- 12 Aug 2024Published
- 19 May 2025Added to CISA KEV (exploited in the wild) · 279 days (about 9 months) later
- 21 May 2025CISA SSVC assessment: exploitation active · 2 days later
- 9 Jun 2025CISA remediation due date (US federal agencies) · 19 days later
- 21 Oct 2025CVE record last updated · 135 days (about 5 months) later
- 2 Nov 2026Analysed by vulneraibility.com · 377 days (about 1 year) later
- Advisorywelivesecurity.com /en/eset-research/operation-roundpress/
- Linkwiki.zimbra.com /wiki/Zimbra_Releases/10.0.7#Security_Fixes
- Linkwiki.zimbra.com /wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes
- Linkcisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443
sources
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
- Nuclei templates: detection templates
- Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.