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18Track

Synacor Zimbra Collaboration: Cross-site scripting

Synacor Zimbra Collaboration · CVE-2026-66911 EUVD-2026-112941
0 news outlets1 CERTs and agencies0 research labs

Assessment: Track

SSVC decision points: exploitation none, automatable no, technical impact partial, deployment low.

What is it?

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

Evidence

Official warnings2National CERTs, government cyber security agencies and the vendor’s own advisories

Exploitation

  • Exploit code published (not verified by us)
  • Exploited in the wild (confirmed by a source)
  • Listed as known exploited (CISA KEV)
CVSS
5.3
EPSS
–
First seen
3 h ago
Status
confirmed

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