← gociux.comall exploited CVEs

Exploited vulnerability · CISA KEV

Is CVE-2025-27915 exploited? Yes: in CISA KEV since 7 Oct 2025

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

Yes. CVE-2025-27915, 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 7 Oct 2025, 209 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 · 7 Oct 2025
ransomwareNot knownno confirmed use
EPSStop 10%more likely than most to be exploited
severity5.4CVSS 3.1 · medium
US federal due28 Oct 2025BOD 22-01 deadline

What it is

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.

VendorSynacor (19 exploited CVEs in KEV)
ProductZimbra Collaboration Suite (ZCS)
VulnerabilitySynacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting Vulnerability
WeaknessCWE-79
Published12 Mar 2025
Added to KEV7 Oct 2025
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 12 Mar 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-2025-27915 being exploited?

Yes. CISA added CVE-2025-27915 to the Known Exploited Vulnerabilities catalog on 7 Oct 2025, which means there is reliable evidence of exploitation in the wild.

Is CVE-2025-27915 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-2025-27915?

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 October 2025 · Synacor scorecard · act-now radar.

Running Synacor in a regulated environment?

We check exposure across your estate, patch or mitigate with your team, and set up detection for what attackers do after exploiting it.

Get in touch →