Vulnerability in Microsoft 365 Copilot Chat

CVE-2026-26164

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

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.010 (63.0th percentile), scored .

Low probability of exploitation in the next 30 days, but still tracked. 63rd percentile — 63.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-26164: held from 0.008 to 0.010.

EPSS over last 30 days · oldest: 0.008 · newest: 0.010 · change: +0.002

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-26164?
CVE-2026-26164 is a high-severity vulnerability in Microsoft 365 Copilot Chat, classified under Improper Neutralization of Special Elements in Output Used by a Downstream Component (Injection). CVSS score: 7.5/10. Published 2026-05-07.
How severe is CVE-2026-26164?
High severity. CVSS v3 base score is 7.5 out of 10.