# Microsoft Security Advisory CVE-2026-40372 – ASP.NET Core Elevation of Privilege Advisory record · `GHSA-9mv3-2cwr-p262` - **Identifiers:** `GHSA-9mv3-2cwr-p262` · `BIT-aspnet-core-2026-40372` · `CVE-2026-40372` - **State:** Confirmed - **Severity:** CVSS 9.1 Critical - **Critical:** Yes: CVSS 9+, CVSS 7+ and EPSS - **Weakness (CWE):** [CWE-347](https://cwe.mitre.org/data/definitions/347.html) - **Tags:** [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) - **Published:** 23 Apr 2026 - **Updated:** 5 May 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 23 Apr 2026, 14:55 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Critical Critical, because: - CVSS score 9.1: 9.0 or more. - CVSS score 9.1 (7.0 or more) and EPSS 0.11 (0.1 or more): a high score and a real chance of exploitation in the next 30 days. How we decide what’s critical: ## Affected packages - `Microsoft.AspNetCore.DataProtection` (NuGet): affected `>=10.0.0, <10.0.7`; fixed in `10.0.7` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > Microsoft.AspNetCore.DataProtection versions 10.0.0 through 10.0.6 from NuGet are affected. An attacker can forge authentication cookies and decrypt some protected payloads, which can lead to elevation of privilege; the source does not describe the required network position or prior access. Upgrade to 10.0.7 or later, then rotate the DataProtection key ring if the application was exposed during the vulnerable window. Written 9 Nov 2026. ## Not analysed yet We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check. ## Severity and exploitation - 9.1 Critical, CVSS 3.1: `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`, from CNA (microsoft) - **CISA KEV:** Not listed. - **EPSS:** 0.11, the 95th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 21 Apr 2026, 18:57 UTC: [Published by the maintainers as a GitHub repository advisory](https://github.com/dotnet/aspnetcore/security/advisories/GHSA-9mv3-2cwr-p262) - 31 Oct 2026, 15:22 UTC: First seen by agentprime - 31 Oct 2026, 15:22 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-9mv3-2cwr-p262) ## Sources - [GitHub Advisory Database: GHSA-9mv3-2cwr-p262](https://github.com/advisories/GHSA-9mv3-2cwr-p262) - [OSV: GHSA-9mv3-2cwr-p262](https://osv.dev/vulnerability/GHSA-9mv3-2cwr-p262) - - - - - Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .