What is CVE-2026-26137?

CVE-2026-26137 is a critical-severity vulnerability in Microsoft 365_copilot_chat, classified under Server-Side Request Forgery (SSRF). CVSS score: 9.9/10. Published 2026-03-19.

How severe is CVE-2026-26137?

Critical severity. CVSS v3 base score is 9.9 out of 10.

SSRF in Microsoft 365_copilot_chat

CVE-2026-26137

Server-side request forgery (ssrf) in Microsoft Exchange allows an authorized attacker to elevate privileges over a network.

Vulnerability class: SSRF (Server-Side Request Forgery)

EPSS: 0.005 (41.8th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L.

Affected products

Microsoft 365_copilot_chat
Microsoft Exchange Online

Weakness classification (CWE)

CWE-918 — Server-Side Request Forgery (SSRF)

References

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

Frequently asked questions

What is CVE-2026-26137?: CVE-2026-26137 is a critical-severity vulnerability in Microsoft 365_copilot_chat, classified under Server-Side Request Forgery (SSRF). CVSS score: 9.9/10. Published 2026-03-19.
How severe is CVE-2026-26137?: Critical severity. CVSS v3 base score is 9.9 out of 10.