9.9

CVE-2026-50517: microsoft 365_copilot Deserialization of Untrusted Data

CVSS: 9.9v3.1CriticalAnalyzed
Published 24-07-2026Last modified 08-10-2026
Open JSON

Vulnerability summary

CVE-2026-50517 is a critical (CVSS 9.9) Deserialization of Untrusted Data vulnerability in microsoft 365_copilot. EPSS estimates a 1.69% chance of exploitation in the next 30 days, higher than 76.8% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.9/10
010
Critical · v3.1 (CVE.org)
EPSS score
1.69%
0%100%
Low · +0.44 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 24-07-2026
    PublishedVulnerability first disclosed.
  2. 08-10-2026
    Last modifiedVulnerability information updated.

Description

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

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

1.69%

Chance of exploitation in the next 30 days

Percentile

77%

Versus all other CVEs

30-day change

+0.44 pp

From 1.25% on 20-09-2026

20-09-202620-10-2026
EPSS score
1.69%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Microsoft2 products

1 vendor · 2 products

References

1 links