CVE detail
CVE-2025-27915: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
Source: CISA Known Exploited Vulnerabilities catalog · back to feed
Vendor / product
Synacor · Zimbra Collaboration Suite (ZCS)
- Date added (KEV)
- Oct 07, 2025
- CISA due date
- Oct 28, 2025
- Ransomware campaign use
- Unknown
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.
Scorifya interpretation
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Plain English
Technical detail
From CISA
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.
https://wiki.zimbra.com/wiki/Security_Center ; https://nvd.nist.gov/vuln/detail/CVE-2025-27915
See what attackers can see on your domain
This vulnerability is on CISA's Known Exploited Vulnerabilities list, so it is being exploited in the wild right now. Scorifya can't test for Synacor directly, but in about 30 seconds it shows what your own domain exposes publicly across TLS, security headers, DNS, and cookies: the surface attackers probe first.
SOC 2 compliance
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See Scorifya Controls →References
- https://wiki.zimbra.com/wiki/Security_CenterRelease Notes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_FixesRelease Notes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_FixesRelease Notes
- https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_FixesRelease Notes
- https://strikeready.com/blog/0day-ics-attack-in-the-wild/ExploitThird Party Advisory
Other recent CVEs from Synacor
- CVE-2025-48700Zimbra Collaboration Suite (ZCS), Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
- CVE-2025-66376Zimbra Collaboration Suite (ZCS), Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting Vulnerability
- CVE-2020-7796Zimbra Collaboration Suite, Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery Vulnerability
- CVE-2025-68645Zimbra Collaboration Suite (ZCS), Synacor Zimbra Collaboration Suite (ZCS) PHP Remote File Inclusion Vulnerability
- CVE-2019-9621Zimbra Collaboration Suite (ZCS), Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery (SSRF) Vulnerability