Live › vulnerability › CVE-2025-27915
Go to dashboardZimbra Collaboration Suite's Classic Web Client does not sanitize HTML in ICS calendar attachments, so a crafted email runs attacker JavaScript when the victim opens it. The script runs in the victim's session and can set mail filters to forward messages to an attacker address and exfiltrate data.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 19:11 UTC, 5h before NVD. All times on this page are UTC.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
| Product | Ecosystem | Affected | Fixed in |
|---|---|---|---|
| Synacor Zimbra Collaboration Suite (ZCS) | vendor | – | – |
| synacor zimbra collaboration suite | vendor | >= 10.0.0, < 10.0.13 | 10.0.13 |
| synacor zimbra collaboration suite | vendor | >= 10.1.0, < 10.1.5 | 10.1.5 |
| synacor zimbra collaboration suite | vendor | = 9.0.0 | – |
Unknown from the sources.
Apply the mitigations from Synacor/Zimbra vendor instructions (CISA KEV entry, no version given in sources); if mitigations are unavailable, discontinue use of the product per CISA guidance.
Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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 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.
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