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CVE-2025-48700

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

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.

CVSS Score
6.1
Medium
EPSS — Exploit Probability
18%
Riskier than 95% of all CVEs
Exploitation
Confirmed in the wild
Used in ransomware campaigns
Remediation
Patch available
Federal deadline 2026-04-23
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. Deadline for federal agencies: 2026-04-23.

NVD entry Vendor patch PoC / advisory CISA KEV

5 articles across 5 outlets · first covered Apr 21, 2026 · latest Apr 21, 2026

Associated threat actors

DEV-0950

Coverage timeline