CVE-2026-40372: exploitation status and patch state

CVE-2026-40372 · CVSS 9.1 CRITICAL · EPSS 11% · patch available

Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized attacker to elevate privileges over a network.

Is CVE-2026-40372 exploited?

• Not in the CISA KEV catalog.
• EPSS puts exploitation in the next 30 days at 11%.
• Public exploit code: none found in monitored sources.

Which products and versions are affected?

No affected package list recorded here yet.

Is there a patch?

• KB5091596
• Release Notes

What PlainSec published about CVE-2026-40372

• RDP Phishing Warning Breaks on Mixed-Scale Monitors (2026-04-25)
• ASP.NET Core Token Forgery Leaves Privileged Sessions Behind (2026-04-23)

Primary sources

• NVD record
• Microsoft KB5091596
• Microsoft Release Notes

What this record does not say

• No affected package data.

KEV and EPSS are re-checked daily. Record last updated 2026-08-11.