CVE-2024-27443

Exp

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.

Published: 2024-08-12 Last update: 2025-10-31 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2024-27443 is rated Critical Active Threat (83.8/100): CVSS Medium severity, with high exploitation likelihood (EPSS 32.88%, 97th percentile). CISA KEV confirms active exploitation (added 2025-05-19) affecting Synacor / Zimbra Collaboration Suite (ZCS). cross-site scripting (CWE-79) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2024-27443

Name: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS) Vulnerability · CISA KEV detail

Exploit added: 2025-05-19

Action due: 2025-06-09

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

Exploit prediction scoring system (EPSS) score for CVE-2024-27443

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-08 32.43% 32.88% +0.45%
2 2026-05-20 29.77% 32.43% +2.66%
3 2026-05-19 — 29.77% —

Full EPSS history (54 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2024-27443

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 [email protected]
6.1 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 2.7 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2024-27443

Affected software / configurations for CVE-2024-27443

Vendor Product Version Raw CPE
zimbra collaboration >= 10.0.0, < 10.0.7 cpe:2.3:a:zimbra:collaboration:*:*:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:-:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p0:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p1:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p10:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p11:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p12:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p13:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p14:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p15:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p16:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p19:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p2:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p20:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p21:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p23:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p24:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p24.1:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p25:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p26:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p27:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p3:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p30:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p31:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p32:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p33:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p34:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p35:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p36:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p37:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p38:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p4:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p5:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p6:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p7:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p7.1:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p8:*:*:*:*:*:*
zimbra collaboration 9.0.0 cpe:2.3:a:zimbra:collaboration:9.0.0:p9:*:*:*:*:*:*

References for CVE-2024-27443

cvelogic Threat Intelligence