(Pwn2Own) Microsoft SharePoint Improper Verification of Cryptographic Signature Remote Code Execution Vulnerability

July 15th, 2026
ZDI-26-413 ZDI-CAN-31261

CVE ID

CVE-2026-50522

CVSS Score

8.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors

Microsoft

Affected Products

SharePoint

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Microsoft SharePoint. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the handling of session security tokens. The issue results from the lack of proper verification of a cryptographic signature. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the service account.

Additional Details

Microsoft has issued an update to correct this vulnerability. More details can be found at:
https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-50522

Disclosure Timeline

  • 2026-05-21 - Vulnerability reported to vendor
  • 2026-07-15 - Coordinated public release of advisory
  • 2026-07-15 - Advisory Updated

Credit

splitline (@_splitline_) from DEVCORE Research Team

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