Medium 5.4Known exploited (CISA KEV)Published Mar 11, 2025

CVE-2025-27915An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1.

Updated under an hour ago (Oct 30, 2026, 3:10 AM ET)

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It affects synacor zimbra_collaboration_suite. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Oct 7, 2025; federal agencies had to remediate by Oct 28, 2025. Treat that date as your deadline.

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Start free and add your stackFree account, 3 products Every CVE for synacor zimbra_collaboration_suite Exploited in the last 30 days

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.

CVSS: 5.4 MEDIUM (v3.1, CISA ADP)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE): CWE-79
Known exploited: Added to CISA KEV Oct 7, 2025; federal remediation due Oct 28, 2025Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS (exploitation in the next 30 days): 4.06% (percentile 91)
Assigned by: mitre
NVD analysis: Analyzed
Record last updated: Feb 26, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

synacor zimbra_collaboration_suite synacor:zimbra_collaboration_suite	from 10.0.0 before 10.0.13; from 10.1.0 before 10.1.5; 9.0.0; 9.0.0; 9.0.0; 9.0.0; 9.0.0; 9.0.0; and 39 more ranges	NVD

References

References

https://wiki.zimbra.com/wiki/Security_Center	release-notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.1.5#Security_Fixes	release-notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/10.0.13#Security_Fixes	release-notes
https://wiki.zimbra.com/wiki/Zimbra_Releases/9.0.0/P44#Security_Fixes	release-notes
https://strikeready.com/blog/0day-ics-attack-in-the-wild/	exploit, third-party-advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-27915	us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.