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PatchSiren cyber security CVE debrief

CVE-2026-93642 Zimbra CVE debrief

An unauthenticated sender can forge a share notification that triggers stored XSS when a signed-in Zimbra Modern recipient clicks Accept Share, allowing the attacker to access mailbox data and act as the victim. This critical vulnerability enables attackers to access mailbox data and act as victims, necessitating prompt verification and mitigation. Defenders should prioritize verifying and mitigating this vulnerability, especially for Zimbra Modern deployments, to prevent potential mailbox data access and unauthorized actions. The CVE record and NVD entry provide details on the vulnerability, but additional information from Zimbra's official security advisories may be necessary for

Vendor
Zimbra
Product
Zimbra Collaboration Suite (ZCS)
CVSS
CRITICAL 9.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-25
Original CVE updated
2026-09-25
Advisory published
2026-09-25
Advisory updated
2026-09-25

Who should care

Defenders responsible for Zimbra Modern deployments, particularly those handling sensitive mailbox data, should assess exposure and prioritize mitigation to prevent potential data breaches and unauthorized actions.

Why it matters

CVE-2026-93642 is a critical stored XSS vulnerability in Zimbra Modern that allows unauthenticated attackers to access mailbox data and act as victims, necessitating prompt verification and mitigation.

  • Potential unauthorized access to mailbox data
  • Possible impersonation of victims
  • Required verification of Zimbra Modern deployments for vulnerability
  • Necessity for input validation and output encoding for share notifications

Technical summary

CVE-2026-93642 is a critical vulnerability in Zimbra Modern that allows unauthenticated attackers to forge share notifications, triggering stored XSS when a signed-in recipient clicks Accept Share. This enables attackers to access mailbox data and act as the victim.

Defensive priority

Defenders should prioritize verifying and mitigating this vulnerability, especially for Zimbra Modern deployments, to prevent potential mailbox data access and unauthorized actions.

Recommended defensive actions

  • Verify Zimbra Modern deployments for vulnerability to CVE-2026-93642
  • Implement input validation and output encoding for share notifications
  • Restrict access to mailbox data and functionality
  • Monitor for suspicious activity and implement incident response plans

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but additional information from Zimbra's official security advisories may be necessary for comprehensive mitigation.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-93642 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-93642

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-93642 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-93642

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.