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CVE-2025-48700: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability

criticalknown exploitedCVE-2025-48700
Actively exploited. At least one CVE in this advisory is listed in the CISA Known Exploited Vulnerabilities catalog — exploitation has been observed in the wild. Treat remediation as urgent.
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.

CSIRTS triage

vendor: Synacorproduct: Zimbra Collaboration Suite (ZCS)Cross-site scripting
What
A cross-site scripting vulnerability could allow attackers to execute arbitrary JavaScript within the user's session.
Who is affected
Users of Synacor Zimbra Collaboration Suite (ZCS).
Urgency
Remediation is urgent as the vulnerability is critical and has been exploited.
Action
Update to the latest version of ZCS.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
CISA Known Exploited Vulnerabilities (US · database · site)
Severity
critical
Published
2026-04-20
Exploitation
Observed in the wild (CISA KEV)

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2025-48700

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2025-48700coverage & exploitation statusNVD · CVE.org

Recent advisories for Synacor Zimbra Collaboration

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

More from CISA Known Exploited Vulnerabilities