CVE-2026-50517
CVE-2026-50517 is a critical deserialization vulnerability in M365 Copilot that allows an authorized attacker to execute arbitrary code over the network. It has a CVSS base score of 9.9 (vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H), indicating high impact on confidentiality, integrity, and availability. No known exploitation or public exploit is currently reported, and no official fix is documented in the provided sources.
No official fix yet. If none appears within 45 days of first tracking, this entry is removed automatically.
Who is affected
M365 Copilot (specific product versions not listed in the sources)
Real-world impact
An attacker with legitimate access could leverage the flaw to run code remotely, potentially compromising the affected system.
Why this severity
The CVSS score of 9.9 reflects a network‑reachable attack requiring low complexity and low privileges, with no user interaction, and resulting in full compromise of confidentiality, integrity, and availability.
What to do about it
No official fix or mitigation is documented in the sources yet. Monitor the vendor advisory and apply the patch as soon as it is released.
No fix documented in sources
Timeline
- Jul 24, 2026 · 8d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 29, 2026 · 3d agoAdvisory updatedThe NVD record was last revised.
How it’s attacked
References & advisories
- msrc.microsoft.com/update-guide/vulnerability/…vendor advisory