---
title: "CVE-2026-40372: Microsoft Security Advisory CVE-2026-40372 – ASP.NET Core Elevation of Privilege"
url: https://erroneo.us/security/cve/CVE-2026-40372/
description: "CVE-2026-40372 (Microsoft.AspNetCore.DataProtection (NuGet)): Improper verification of cryptographic signature in ASP.NET Core allows an unauthorized…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-04-21
date_modified: 2026-10-15
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-40372"
kev: false
cvss: 9.1
epss: 0.00824
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-40372: Microsoft Security Advisory CVE-2026-40372 – ASP.NET Core Elevation of Privilege

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.8% , percentile 57: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 57% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes Microsoft.AspNetCore.DataProtection (NuGet) >= 10.0.0, <= 10.0.6, fixed in 10.0.7 . Check your lockfile, including transitive dependencies.

## What it is

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

## Affected packages

- NuGet `Microsoft.AspNetCore.DataProtection` >= 10.0.0, <= 10.0.6 → fixed: 10.0.7

## Affected products (CVE record)

- Microsoft ASP.NET Core 10.0: 10.0 < 10.0.7
- Microsoft Microsoft Visual Studio 2026 version 18.5: 18.5.0 < 18.5.2

## Severity

- microsoft CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C`
- redhat-SADP CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`
- GitHub CVSS 3.1: 9.1 `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.82% probability of exploitation activity in the next 30 days; percentile 57.

## Sources

- [ASP.NET Core Elevation of Privilege Vulnerability](https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40372)
- [GitHub Advisory GHSA-9mv3-2cwr-p262](https://github.com/advisories/GHSA-9mv3-2cwr-p262)
- [CVE.org record CVE-2026-40372](https://www.cve.org/CVERecord?id=CVE-2026-40372)
- [NVD entry CVE-2026-40372](https://nvd.nist.gov/vuln/detail/CVE-2026-40372)
- [access.redhat.com](https://access.redhat.com/security/cve/CVE-2026-40372)
- [RHBZ#2460224](https://bugzilla.redhat.com/show_bug.cgi?id=2460224)
- [security.access.redhat.com](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40372.json)
- [github.com](https://github.com/dotnet/aspnetcore/security/advisories/GHSA-9mv3-2cwr-p262)
- [github.com](https://github.com/dotnet/announcements/issues/395)

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Source page: https://erroneo.us/security/cve/CVE-2026-40372/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt