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CVE-2026-66911

Stored Cross-Site Scripting in Zimbra

No known exploitation. No EPSS score yet. Fixed in 10.1.21.

CVSS —Not scoredEPSS percentile—No score yetCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix10.1.21Upgrade to this build

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • Synacor Zimbra CollaborationAffected: < 10.1.21Upgrade to: 10.1.21Stated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

Zimbra is vulnerable to stored cross-site scripting (XSS) via the Content-Location MIME header in email attachments. Due to lack of sanitization of the Content-Location header, an attacker can set it to a javascript: URI. An unauthenticated remote attacker can send a crafted email to a victim; when the victim opens the email in the Zimbra web interface and clicks the attachment name, the JavaScript payload executes in the victim's browser context. This issue was fixed in version 10.1.21

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

No EPSS score yet. New CVEs are usually scored within a few days.

Lifecycle

5 events over 7 days, from the signal feeds we watch.

  1. Publishedweakness classified, att&ck mapped, record updated
  2. OpenVAS check added

Affected products

Technical detail

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

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We'll flag the next CVE, public exploit or patch for Zimbra Collaboration, not every advisory.