What is CVE-2026-26129?

CVE-2026-26129 is a high-severity vulnerability in Microsoft 365_copilot_chat, classified under CWE-138. CVSS score: 7.5/10. Published 2026-05-07.

How severe is CVE-2026-26129?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Microsoft 365_copilot_chat

CVE-2026-26129

Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.

EPSS: 0.001 (17.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Affected products

Microsoft 365_copilot_chat
Microsoft 365 Copilot's Business Chat

Weakness classification (CWE)

CWE-138

References

secure@microsoft.com (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-26129?: CVE-2026-26129 is a high-severity vulnerability in Microsoft 365_copilot_chat, classified under CWE-138. CVSS score: 7.5/10. Published 2026-05-07.
How severe is CVE-2026-26129?: High severity. CVSS v3 base score is 7.5 out of 10.