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CVE-2026-78501: Microsoft 365 Copilot Business Chat Information Disclosure Vulnerability

• Severity: high (CVSS 8.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-10-31
• Weakness: CWE-77

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.

Affected products

• Microsoft 365 Copilot's Business Chat: all versions
• Microsoft 365 Copilot's Business Chat: all versions

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-78501

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