What is CVE-2026-50517?

CVE-2026-50517 is a critical-severity vulnerability in Microsoft 365 Copilot, classified under Deserialization of Untrusted Data. CVSS score: 9.9/10. Published 2026-07-24.

How severe is CVE-2026-50517?

Critical severity. CVSS v3 base score is 9.9 out of 10.

Deserialization in Microsoft 365 Copilot

CVE-2026-50517

Deserialization of untrusted data in M365 Copilot allows an authorized attacker to execute code over a network.

Vulnerability class: Insecure Deserialization

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

Affected products

Microsoft 365 Copilot

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

secure@microsoft.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-50517?: CVE-2026-50517 is a critical-severity vulnerability in Microsoft 365 Copilot, classified under Deserialization of Untrusted Data. CVSS score: 9.9/10. Published 2026-07-24.
How severe is CVE-2026-50517?: Critical severity. CVSS v3 base score is 9.9 out of 10.