CVE-2025-27915
Synacor Zimbra Collaboration Suite (ZCS): Cross-site Scripting
As of , CVE-2025-27915 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 7 October 2025
- US federal deadline
- 28 October 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
- 0.04Higher than 90% 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
Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
CISA's description
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.
The CVE record's description, from mitre
- CVE published
- 12 March 2025
- Assigned by
- mitre
- CVSS
- 5.4 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
- The CVE record was published.
- CISA added it to its list of exploited vulnerabilities.
- The US federal deadline to fix it.
Zimbra Collaboration Suite (ZCS): other exploited entries
| Vulnerability | Product | Our group | Listed | Deadline | EPSS |
|---|---|---|---|---|---|
| CVE-2026-73570OS Command Injection | Synacor Zimbra Collaboration Suite (ZCS) | Patch nowForensic triage required by CISA | 0.72 | ||
| CVE-2019-9621Server-Side Request Forgery (SSRF) | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekMetasploit module; EPSS 0.81; verified Exploit-DB entry | 0.81 | ||
| CVE-2019-9670Improper Restriction of XML External Entity Reference | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekMetasploit module; EPSS 0.99; verified Exploit-DB entry | 0.99 | ||
| CVE-2022-41352Arbitrary File Upload | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekRansomware use; Metasploit module; EPSS 0.95 | 0.95 | ||
| CVE-2022-27925Arbitrary File Upload | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekRansomware use; Metasploit module; EPSS 0.99 | 0.99 | ||
| CVE-2022-37042Authentication Bypass | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekRansomware use; Metasploit module; EPSS 0.92 | 0.92 | ||
| CVE-2023-34192Cross-Site Scripting (XSS) | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekEPSS 0.77 | 0.77 | ||
| CVE-2024-45519Command Execution | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekEPSS 0.99 | 0.99 | ||
| CVE-2022-27924Command Injection | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekRansomware use; EPSS 0.94 | 0.94 | ||
| CVE-2018-6882Cross-Site Scripting (XSS) | Synacor Zimbra Collaboration Suite (ZCS) | Patch this weekRansomware use | 0.30 |
Read further
- CVE recordcve.org
- NVD entrynvd.nist.gov
- CISA's catalogcisa.gov
- EPSS for this CVEapi.first.org