Microsoft M365 Copilot Remote Code Execution Vulnerability

published 2026-07-24 3 mo ago modified 2026-11-01 7 d ago also EUVD-2026-48457

cvss: 9.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.7%; EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits: 0; none known

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

Patch / fix

links 1

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-50517 advisory

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: total
Assessed: 3 mo ago (2026-07-24)

Exploit prediction

1.69% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	9.9	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA	3.1	9.9	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

Microsoft Microsoft 365 Copilot

Classification

Weakness

CWE-502 Deserialization of Untrusted Data

References

msrc.microsoft.com /update-guide/vulnerability/CVE-2026-50517
vendor-advisory, patch

Sources

CVE List CVE-2026-50517
NVD CVE-2026-50517

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary