# CVE-2026-40372: ASP.NET Core Elevation of Privilege Vulnerability

> An attacker can elevate privileges by exploiting improper cryptographic signature verification in ASP.NET Core.

- **Severity:** Critical 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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** BIT-aspnet-core-2026-40372, GHSA-9mv3-2cwr-p262, UBUNTU-CVE-2026-40372

## What is CVE-2026-40372?

CVE-2026-40372 is a critical authentication bypass vulnerability in Microsoft ASP.NET Core 10.0, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-40372?

3 open source packages ship an affected version, including Microsoft.AspNetCore.DataProtection and aspnet-core. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Microsoft.AspNetCore.DataProtection` | NuGet | From 10.0.0 | 10.0.7 |
| `Microsoft.AspNetCore.DataProtection` | NuGet | From 10.0.0 | 10.0.7 |
| `aspnet-core` | Bitnami | From 10.0.0 | 10.0.7 |

Products: Microsoft Asp.net Core.

## How do I fix CVE-2026-40372?

Upgrade Microsoft.AspNetCore.DataProtection to 10.0.7 or later.

## Is CVE-2026-40372 being exploited?

There is no known exploitation of CVE-2026-40372 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft ASP.NET Core 10.0

- [CVE-2025-55315](https://insights.sbomify.com/CVE-2025-55315/): ASP.NET Security Feature Bypass Vulnerability (critical 9.9)
- [CVE-2026-88092](https://insights.sbomify.com/CVE-2026-88092/): ASP.NET Core Tampering Vulnerability (critical 9.4)
- [CVE-2021-43877](https://insights.sbomify.com/CVE-2021-43877/): ASP.NET Core and Visual Studio Elevation of Privilege Vulnerability (high 8.8)
- [CVE-2020-0603](https://insights.sbomify.com/CVE-2020-0603/): Remote code execution in ASP.NET Core (high 8.8)
- [CVE-2019-1302](https://insights.sbomify.com/CVE-2019-1302/): Elevation of privilege in ASP.NET Core (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40372 and fix it if it is affected.

What it is: CVE-2026-40372 is a critical authentication bypass vulnerability in Microsoft ASP.NET Core 10.0, published on 21 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40372 in the wild and no public exploit code.

Affected packages and fixed versions:
- Microsoft.AspNetCore.DataProtection (NuGet): affected from 10.0.0; fixed in 10.0.7
- Microsoft.AspNetCore.DataProtection (NuGet): affected from 10.0.0; fixed in 10.0.7
- aspnet-core (Bitnami): affected from 10.0.0; fixed in 10.0.7

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40372/ (Markdown: https://insights.sbomify.com/CVE-2026-40372/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40372
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40372
- OSV: https://osv.dev/vulnerability/CVE-2026-40372

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40372/
Summaries are generated and may contain mistakes; the official description above is the record.