CVE-2026-50517: Deserialization of untrusted data in M365 Copilot allows an authorized attacker to execute code over a network.

criticalCVSS 9.9CVE-2026-50517

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

Details

Source: NVD Recent CVEs (US · database · site)
Severity: critical — CVSS 9.9
Published: 2026-07-24
Last updated: 2026-07-29
Exploitation: Not in CISA KEV at last sync

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

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Moderate exploitation riskCVE-2026-505171.3% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 67% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-50517	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

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