CVE-2024-27443An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the…
- 6.1MediumCVSS base score
- 24.6%Exploitation in 30 daysEPSS · top 2.1% of all CVEs
- YesKnown exploitedin CISA's KEV since 19 May 2025
- 1Public exploitsMetasploit, Nuclei and Exploit-DB
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.
Exploited in the wild
CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability.
- Added
- 19 May 2025
- Fix due (US federal)
- 9 Jun 2025
- Used by ransomware
- Not known
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
ENISA's EU Vulnerability Database lists it as exploited, from CISA's KEV, since 19 May 2025.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. The public collections list a Nuclei template for it. CISA's SSVC rates its exploitation: it is being exploited.
Show the exploits1
Nuclei templates1 template
- Zimbra Collaboration - Cross-Site Scripting (XSS) (Nuclei template) (opens in a new tab)
http/cves/2024/CVE-2024-27443.yamlSeverity medium
Modules, templates and exploits as listed by the Metasploit Framework (BSD-3-Clause), ProjectDiscovery's Nuclei templates (MIT) and the Exploit Database (GPLv2), read once a day. Where the data comes from
Timeline
ID reserved
By mitre
- 6 months later
· 6 months later
Published
- 9 months later
· 9 months later
Added to CISA KEV
Known exploited in the wild
- 5 months later
· 5 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CISA-ADPADP (enrichment) | 3.1 | Medium6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| NVDNVD · Analyzed | 3.1 | Medium6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
- EPSS (exploitation in 30 days)
- 24.6% · top 2.1% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: active · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.1.
Affected products
n/a
- affected n/a
References
References4
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.7#Security_Fixes (opens in a new tab)
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P39#Security_Fixes (opens in a new tab)
- https://www.welivesecurity.com/en/eset-research/operation-roundpress/ (opens in a new tab)third-party-advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2024-27443 (opens in a new tab)government-resource
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- CISA KEV catalog (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2024-24646 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2024-27443)Record last updated .