Reference page — cumulative record through Thursday, October 8, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-78501

CVE-2026-78501HIGH

Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  C  H  N  N    8.6   .0089   58.2     —

AFFECTED
  Product                                Versions  Fixed
  Microsoft 365 Copilot's Business Chat  - –       —

TIMELINE
  Aug 24  Reserved by microsoft
  Sep 17  Published (CNA: microsoft)
  Oct 7   RESCORED — CVE-2026-78501 (Microsoft 365 Copilot's Business Chat). CVSS 7.4 → 8.6 (NVD).

CWE-77, CWE-923 · CNA: microsoft · CVSS v3.1 · 1 reference · NVD status: Analyzed

Description

Improper neutralization of special elements used in a command ('command injection') in Microsoft 365 Copilot's Business Chat allows an unauthorized attacker to disclose information over a network.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
August 24, 2026	Reserved	Reserved by microsoft
September 17, 2026	Published	Published (CNA: microsoft)
October 7, 2026	RESCORED	RESCORED — CVE-2026-78501 (Microsoft 365 Copilot's Business Chat). CVSS 7.4 → 8.6 (NVD).

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Microsoft	Microsoft 365 Copilot's Business Chat	—	-	—

Weaknesses

CWE-77 · CWE-923

References (1)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78501 [Patch, Vendor Advisory]

Authoritative record: CVE-2026-78501 at cve.org

Vendors: microsoft

Weaknesses: CWE-77 · CWE-923

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-78501 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Thursday, October 8, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.