What is CVE-2026-59118?

CVE-2026-59118 is a critical-severity vulnerability in Microsoft Copilot Cowork, classified under Improper Authorization. CVSS score: 9.3/10. Published 2026-08-07.

How severe is CVE-2026-59118?

Critical severity. CVSS v3 base score is 9.3 out of 10.

Auth bypass in Microsoft Copilot Cowork

CVE-2026-59118

Improper authorization in Copilot Cowork allows an unauthorized attacker to elevate privileges over a network.

Published 2026-08-07 · last modified 2026-10-24.

CVSS v3 metric

CVSS v3 base score 9.3 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (53.8th percentile), scored 2026-11-04.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 53.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-285 — Improper Authorization

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59118 (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-59118?: CVE-2026-59118 is a critical-severity vulnerability in Microsoft Copilot Cowork, classified under Improper Authorization. CVSS score: 9.3/10. Published 2026-08-07.
How severe is CVE-2026-59118?: Critical severity. CVSS v3 base score is 9.3 out of 10.