# CVE-2026-123384

Heap buffer overflow in Outlook allows remote code execution.

- Page: https://www.vulneraibility.com/cve/CVE-2026-123384
- CVSS: 8.8
- Known exploited: not in CISA KEV as of our last sync
- EPSS: 0.84% (percentile 58.2)
- CISA SSVC: exploitation none, automatable no, technical impact total (assessed 2026-11-10)
- Weakness: CWE-122
- Published: 2026-11-10

## Affected versions

- Microsoft Microsoft 365 Apps for Enterprise: affected >= 16.0.1 and < https://aka.ms/OfficeSecurityReleases
- Microsoft Microsoft Office LTSC 2021: affected >= 16.0.1 and < 16.0.14334.21048
- Microsoft Microsoft Office LTSC 2024: affected >= 16.0.0 and < 16.0.17932.21140

A version outside these ranges is not a statement that it is unaffected.

## Impact

Remote code execution via crafted email/attachment, enabling arbitrary code in the Outlook process, malware delivery and persistence.

## Action

Immediate action required

## Recommendation

Install Microsoft update now; block/scan attachments; enable EDR and monitoring.

## References

- [patch] https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-123384

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.