CriticalVulnerability

CVE-2026-50517: M365 Copilot deserialization of untrusted data over a network

Source: NVD(opens in a new tab)
Identifier: CVE-2026-50517
Published: July 23, 2026
Record updated: October 9, 2026

Known exploitation: Not listed in the CISA Known Exploited Vulnerabilities catalog at the last check.
EPSS: 1.7%

Summary

CVE-2026-50517 is a deserialization of untrusted data flaw (CWE-502) in M365 Copilot. The source says an authorized attacker can exploit it over a network to execute code. NVD has not yet provided an assessment, and the source lists Microsoft Corporation as the CVE source.

Mitigation

The source does not state a fix yet. Check the original advisory for updates.

Details

Scores and exploitation

CVSS score: 9.9(critical)
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Attack vector: network
Attack complexity: low
Privileges required: low
User interaction: none
EPSS: 1.7%Estimated probability that this CVE is exploited in the next 30 days, from the FIRST Exploit Prediction Scoring System. Read on November 4, 2026.
Disclosure date: July 23, 2026

Weaknesses and techniques

Weakness (CWE): CWE-502
Attack pattern (CAPEC): CAPEC-586

Affected

Vendors: Microsoft

Classification

Attack type: Other
Attack sophistication: Moderate
AI component targeted: Plugin
Impact: Confidentiality,
Integrity,
Availability
Labels: security

How this record was produced

Summaries, mitigations and labels on this page are generated automatically from the source. The linked source is authoritative. The source gives this advisory a description and no title, so the title above is a headline generated from the source text.

Original source: https://nvd.nist.gov/vuln/detail/CVE-2026-50517

First tracked: July 24, 2026 at 02:09 AM ET, from NVD/CVE Database

Classifier: claude-haiku-5-5, prompt v4

Classifier confidence: 85% (self-assessed)

Topics

Coding assistants

Summary

Mitigation

Topics

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