# Microsoft Security Advisory CVE-2026-62899 – .NET Security Feature Bypass Vulnerability

Advisory record · `GHSA-r6mh-95jw-g7qg`

- **Identifiers:** `GHSA-r6mh-95jw-g7qg` · `BIT-dotnet-2026-62899` · `BIT-dotnet-sdk-2026-62899` · `CVE-2026-62899`
- **State:** Confirmed
- **Severity:** CVSS 5.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-444](https://cwe.mitre.org/data/definitions/444.html)
- **Tags:** [HTTP request smuggling](https://agentprime.io/advisories/tag/request-smuggling.md)
- **Published:** 11 Aug 2026
- **Updated:** 17 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 11 Aug 2026, 18:40 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `Microsoft.NETCore.App.Runtime.linux-arm` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.linux-arm64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.linux-musl-arm` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.linux-musl-arm64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.linux-musl-x64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.linux-x64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.osx-arm64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`
- `Microsoft.NETCore.App.Runtime.osx-x64` (NuGet): affected `>=10.0.0, <10.0.11 || >=9.0.0, <9.0.19 || >=8.0.0, <8.0.30`; fixed in `10.0.11`, `9.0.19`, `8.0.30`

## 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

- 5.9 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C`, from CNA (microsoft)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0075, the 55th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:21 UTC: First seen by agentprime
- 31 Oct 2026, 15:21 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-r6mh-95jw-g7qg)

## Sources

- [GitHub Advisory Database: GHSA-r6mh-95jw-g7qg](https://github.com/advisories/GHSA-r6mh-95jw-g7qg)
- [OSV: GHSA-r6mh-95jw-g7qg](https://osv.dev/vulnerability/GHSA-r6mh-95jw-g7qg)
- <https://github.com/dotnet/runtime/security/advisories/GHSA-r6mh-95jw-g7qg>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-62899>
- <https://github.com/dotnet/announcements/issues/427>
- <https://github.com/dotnet/runtime>
- <https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62899>

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 (<https://api.agentprime.io/mcp>), 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: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-r6mh-95jw-g7qg>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-r6mh-95jw-g7qg/>. Everything for agents: <https://agentprime.io/llms.txt>.