CVE-2026-26129Critical
M365 Copilot Information Disclosure Vulnerability
Assessment
Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.
- Severity
- Critical
- CVSS base score
- 7.5CVSS:3.1/
AV:N/ AC:L/ PR:N/ UI:N/ S:U/ C:H/ I:N/ A:N/ E:U/ RL:O/ RC:C - Impact
- Information Disclosure
- EPSS, next 30 days
- 1.0%Higher than 62.2% of scored CVEs · FIRST model run 29 Sep 2026 · about EPSS
- Public exploit code
- No Nuclei template lists it
- Exploitability
- Not assessed
- Publicly disclosed
- No
- Customer action
- Not required (service-side fix)
- Component
- M365 Copilot
- Weakness
- CWE-138: Improper Neutralization of Special Elements
- Issued by
- Microsoft
- Published
- 7 May 2026 · May 2026
- Last revised
- 7 May 2026
Updates that fix it
0 KBsNo KB listed
MSRC lists no downloadable update, which usually means a service-side fix or a release-notes update. Check the MSRC advisory.
Affected products
Apps1 affected product
- Microsoft 365 Copilot's Business Chat