CVE-2026-26164: high-severity vulnerability in Microsoft 365 Copilot's Business Chat
M365 Copilot Information Disclosure Vulnerability
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.8%
Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
Affected products
Microsoft · Microsoft 365 Copilot's Business ChatRelated CVEs — Microsoft 365 Copilot's Business Chat
In the same product, most dangerous first.
CVE-2026-26129HIGHM365 Copilot Information Disclosure VulnerabilityEPSS 1.1%CVE-2025-53787HIGHMicrosoft 365 Copilot BizChat Information Disclosure VulnerabilityEPSS 0.7%CVE-2025-53774MEDIUMMicrosoft 365 Copilot BizChat Information Disclosure VulnerabilityEPSS 0.6%CVE-2025-59286CRITICALCopilot Information Disclosure VulnerabilityEPSS 0.6%CVE-2025-59272CRITICALCopilot Information Disclosure VulnerabilityEPSS 0.6%CVE-2026-78501HIGHMicrosoft 365 Copilot Business Chat Information Disclosure VulnerabilityEPSS 0.5%