# CVE-2026-102866: Microsoft Office SharePoint cryptographic signature verification bypass

Source: https://junglewise.ai/threats/cve-2026-102866-improper-verification-of-cryptographic-signature-in-microsoft  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-13. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-102866 · Severity: high · CVSS 8.1 · Published 2026-10-13

Microsoft Office SharePoint, a collaboration platform used by enterprises to share documents and manage content, contains a flaw in how it verifies digital signatures on content. An attacker can exploit this flaw over the network to gain elevated privileges and potentially access sensitive information or take unauthorized actions within SharePoint.

Technologies: [Microsoft Office SharePoint](https://junglewise.ai/threats/technologies/office-sharepoint), [Microsoft SharePoint Server](https://junglewise.ai/threats/technologies/sharepoint-server). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2026-102866 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102866 being exploited in the wild.

**How severe is CVE-2026-102866?** High severity, with a CVSS score of 8.1, published 13 October 2026.

**Which products and versions are affected?** Microsoft Office SharePoint.

**Is there a fix for CVE-2026-102866?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-102866 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-102866?** Check whether you run Microsoft Office SharePoint or Microsoft SharePoint Server. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an improper verification of cryptographic signatures in Microsoft Office SharePoint that allows privilege escalation. The flaw can be exploited over a network without requiring prior authentication. An attacker can leverage this to gain higher-level permissions and potentially compromise data integrity or availability.

## Affected products

- Microsoft Office SharePoint

## Timeline

- 2026-10-13: disclosed

## References

- [https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-102866](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-102866)

## Related threats

- [Microsoft Office SharePoint privilege escalation via missing authorization](https://junglewise.ai/threats/cve-2026-88176-missing-authorization-in-microsoft-office-sharepoint-allows-an)
- [Microsoft Office SharePoint XSS privilege escalation](https://junglewise.ai/threats/cve-2026-80095-improper-neutralization-of-input-during-web-page-generation-cross)
- [Microsoft Office SharePoint server-side request forgery](https://junglewise.ai/threats/cve-2026-124210-server-side-request-forgery-ssrf-in-microsoft-office-sharepoint)
- [Microsoft Office SharePoint privilege escalation via incorrect authorization](https://junglewise.ai/threats/cve-2026-123391-incorrect-authorization-in-microsoft-office-sharepoint-allows-an)
- [Microsoft Office SharePoint deserialization of untrusted data](https://junglewise.ai/threats/cve-2026-123390-deserialization-of-untrusted-data-in-microsoft-office-sharepoint)