CVE-2024-27443

Synacor Zimbra Collaboration Suite (ZCS): Cross-Site Scripting (XSS)

As of , CVE-2024-27443 in Synacor Zimbra Collaboration Suite (ZCS) is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch soon.

Exploited
Yes: CISA listed it on 19 May 2025
US federal deadline
9 June 202521 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.24Higher than 97% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
Public exploit
None foundNeither Metasploit nor Exploit-DB lists one.
Fix
Vendor advice: wiki.zimbra.comLinks below, from CISA's entry.

What CISA says to do

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

CISA's required action

What the flaw is

Zimbra Collaboration contains a cross-site scripting (XSS) vulnerability in the CalendarInvite feature of the Zimbra webmail classic user interface. An attacker can exploit this vulnerability via an email message containing a crafted calendar header, leading to the execution of arbitrary JavaScript code.

CISA's 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.

The CVE record's description, from mitre

CVE published
12 August 2024
Assigned by
mitre
CVSS
6.1 Medium (CVSS 3.1, from CISA-ADP)
CWE-79
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Zimbra Collaboration Suite (ZCS): other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2026-73570OS Command InjectionSynacor Zimbra Collaboration Suite (ZCS)Patch nowForensic triage required by CISA0.72
CVE-2019-9621Server-Side Request Forgery (SSRF)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekMetasploit module; EPSS 0.81; verified Exploit-DB entry0.81
CVE-2019-9670Improper Restriction of XML External Entity ReferenceSynacor Zimbra Collaboration Suite (ZCS)Patch this weekMetasploit module; EPSS 0.99; verified Exploit-DB entry0.99
CVE-2022-41352Arbitrary File UploadSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.950.95
CVE-2022-27925Arbitrary File UploadSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.990.99
CVE-2022-37042Authentication BypassSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; Metasploit module; EPSS 0.920.92
CVE-2023-34192Cross-Site Scripting (XSS)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekEPSS 0.770.77
CVE-2024-45519Command ExecutionSynacor Zimbra Collaboration Suite (ZCS)Patch this weekEPSS 0.990.99
CVE-2022-27924Command InjectionSynacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use; EPSS 0.940.94
CVE-2018-6882Cross-Site Scripting (XSS)Synacor Zimbra Collaboration Suite (ZCS)Patch this weekRansomware use0.30

All 17 entries for Zimbra Collaboration Suite (ZCS)

Read further