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Exploited vulnerability · CISA KEV

Is CVE-2025-48700 exploited? Yes: in CISA KEV since 20 Apr 2026

Gociux · Synacor Zimbra Collaboration Suite (ZCS) · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2025-48700, Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 20 Apr 2026, 301 days after it was published. It affects Synacor Zimbra Collaboration Suite (ZCS). If you run it, CISA's required action is: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

exploitedYesCISA KEV · 20 Apr 2026
ransomwareNot knownno confirmed use
EPSSbelow top 10%lower predicted activity right now (it is still confirmed exploited)
severity6.1CVSS 3.1 · medium
US federal due23 Apr 2026BOD 22-01 deadline

What it is

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.

VendorSynacor (19 exploited CVEs in KEV)
ProductZimbra Collaboration Suite (ZCS)
VulnerabilitySynacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
WeaknessCWE-79
Published23 Jun 2025
Added to KEV20 Apr 2026
Reported by (CNA)mitre

What to do

  1. Check whether you run it. Look for Zimbra Collaboration Suite (ZCS) in your asset inventory, including appliances and cloud images. Stack check lists every exploited Synacor CVE at once.
  2. Apply the fix. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 23 Jun 2025.
  4. Get told next time. Email alerts when CISA adds a CVE for Synacor.

Other exploited CVEs in Zimbra Collaboration Suite (ZCS)

References

Questions

Is CVE-2025-48700 being exploited?

Yes. CISA added CVE-2025-48700 to the Known Exploited Vulnerabilities catalog on 20 Apr 2026, which means there is reliable evidence of exploitation in the wild.

Is CVE-2025-48700 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2025-48700?

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Check Synacor's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Zimbra Collaboration Suite (ZCS) and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in April 2026 · Synacor scorecard · act-now radar.

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