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)

Published 2026-03-19 · last modified 2026-06-17.

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.

EPSS exploit prediction

EPSS: 0.007 (54.0th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002

Affected products

Weakness classification (CWE)

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

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26137 (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.