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TI-2026-82516 Aliases CVE-2026-66911GHSA-4r7g-97vg-fv7w

Stored cross-site scripting in Zimbra via email attachments

Priority LOW 25CWE-79Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Passive
Attack complexity
Low
Attack requirements
None
Impact type
Cross-site scripting
Confidentiality · integrity · availability
None · None · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-79.

Summary

Zimbra Collaboration from 0 before 10.1.21 is affected. Zimbra does not sanitize the Content-Location MIME header in email attachments, which is a cross-site scripting flaw (CWE-79). An unauthenticated remote attacker can send a crafted email, and when a victim opens it in the Zimbra web interface and clicks the attachment name, JavaScript runs in the victim's browser.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

Description from the CNA

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

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0054 45th percentileScored 2026-11-07
Fix Fixed Zimbra Collaboration (Synacor): 10.1.21

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
SynacorZimbra Collaborationbefore 10.1.2110.1.21Patch availableCNA
  • Zimbra Collaboration VendorSynacor Affected before 10.1.21 Fixed in 10.1.21 Patch available CNA

Remediation

Upgrade Zimbra Collaboration to version 10.1.21.

Written with Claude Haiku 5.5 from the sources below · 2026-11-05

  • Fix · CNA Zimbra Collaboration (Synacor) Fixed in 10.1.21

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    Synacor Zimbra Collaboration 10.1.21

    2 records Highest priority Priority LOW 2 LOW

    Other records, highest priority first

    • TI-2026-82517 Stored cross-site scripting in Zimbra Collaboration via From headerPriority LOW 24
    Show all 2 records →

Timeline

  1. 2026-10-29 Threatist record created from CVE-2026-66911
  2. 2026-10-29 Alias added: GHSA-4r7g-97vg-fv7w
  3. 2026-11-05 CISA SSVC decision points changed

References

Advisory 1

Other 1

  • TI-2024-30554 The postjournal service in Zimbra Collaboration (ZCS) before 8.8.15 Patch 46, 9 before… KEVCVSS 3.1CRITICAL 10.0
  • TI-2022-19841 An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15 and 9.0. KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-17239 Zimbra Collaboration Suite (ZCS) 8.8.15 and 9.0 has mboximport functionality that… KEVCVSS 3.1CRITICAL 9.8
  • TI-2022-10792 Zimbra Collaboration (aka ZCS) 8.8.15 and 9.0 allows an unauthenticated attacker to… KEVCVSS 3.1CRITICAL 9.8
  • TI-2020-06312 Zimbra Collaboration Suite (ZCS) before 8.8.15 Patch 7 allows SSRF when WebEx zimlet is… KEVCVSS 3.1CRITICAL 9.8
  • TI-2019-07076 mailboxd component in Synacor Zimbra Collaboration Suite 8.7.x before 8.7.11p10 has an… KEVCVSS 3.1CRITICAL 9.8
See all 105 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences