Critical CVSS 9.3 EPSS 0.0039 2026-04 archive

Executive Summary

Url redirection to untrusted site ('open redirect') in M365 Copilot allows an unauthorized attacker to elevate privileges over a network.

Overview

9.3
CVSS CRITICAL
Critical
MS Severity
Not Exploited
MS Exploit Status
N/A
MS Exploit Likelihood
Category Elevation of Privilege
Released Apr 14 2026
Last Updated Apr 14 2026
Publicly Disclosed No
CISA KEV Not Listed
Known Exploits None Known
EPSS Score 0.0039 — 0.30627 percentile
NVD CVSS 9.3 CRITICAL — matches MSRC

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N/E:U/RL:O/RC:C
ATTACK VECTOR
Network
ATTACK COMPLEXITY
Low
PRIVILEGES REQUIRED
None
USER INTERACTION
Required
SCOPE
Changed
CONFIDENTIALITY
High
INTEGRITY
High
AVAILABILITY
None
EXPLOIT CODE MATURITY
Unproven
REMEDIATION LEVEL
Official Fix
REPORT CONFIDENCE
Confirmed
Temporal Score: 8.1

EPSS Score

0.0039
probability of exploitation in the next 30 days
0.30627 percentile - updated 2026-06-21
View on FIRST.org

Known Exploits

Acknowledgments

Henrique Pereira with Microsoft, Rodrigo Silva with Microsoft, Bushra Aloraini with Microsoft