IRONSMITHINTEL
MEDIUMCVSS6.1
|
Actively Exploited
|CISA KEV|CVE-2025-48700|Auth: none — unauthenticated|Reboot: required|Manual only

Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

Synacor Zimbra Collaboration Suite (ZCS) contains a cross-site scripting vulnerability that could allow attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information.

Published Jun 23, 2025 · Updated May 16, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve partial data exposure, partial data tampering. Federal agencies are required to remediate by 2026-04-23 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Cross-Site Scripting (XSS) (CWE-79) vulnerability in Synacor Zimbra Collaboration Suite (ZCS). An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0 and 10.0 and 10.1. A Cross-Site Scripting (XSS) vulnerability in the Zimbra Classic UI allows attackers to execute arbitrary JavaScript within the user's session, potentially leading to unauthorized access to sensitive information. This issue arises from insufficient sanitization of HTML content, specifically involving crafted tag structures and attribute values that include an @import directive and other script injection vectors. The vulnerability is triggered when a user views a crafted e-mail message in the Classic UI, requiring no additional user interaction. Exploitation requires remote network access, low attack complexity, no authentication required, and user interaction required.

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Phishing link

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security
●Running zimbra collaboration suite: 10.0.0 ≤ v < 10.0.12, 10.1.0 ≤ v < 10.1.4, 8.8.15, 9.0.0
Real-world incidentsWhat we've seen

CISA added this CVE to the Known Exploited Vulnerabilities catalog on 2026-04-20 based on evidence of active exploitation in the wild. Federal agencies required to remediate by 2026-04-23.

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

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.

References

    1
    Vendor advisory: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
    1
    NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2025-48700
    1
    CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-48700
PowerShell automationComing soon

No tested PowerShell script for this entry yet. We’re prioritising automation based on user demand.

References

↗ CVE-2025-48700↗ NVD↗ Vendor Advisory