Microsoft Security Advisory CVE-2026-70179 - ASP.NET Core Elevation of Privilege Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-70179: 0.63% estimated exploitation activity in the next 30 days; percentile 50.21 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft.AspNetCore.Authentication.Negotiate. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. ASP.NET Core Negotiate LDAP authentication can associate an authenticated identity with an unintended LDAP principal when the LDAP result is not verified against the Kerberos principal SID. Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/458 CVSS Details - Version: 3.1 - Severity: High - Score: 7.5 - Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H - Weakness: CWE-290 (Authentication Bypass by Spoofing) Affected Platforms - Platforms: Windows, Linux, macOS when LDAP claim resolution is enabled - Architectures: All <a name="affected-packages"</aAffected Packages The vulnerability affects Microsoft .NET projects that use an affected package version…

Published by the source

13 Oct 2026, 20:50 UTC

Last modified by the source

19 Oct 2026, 19:30 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vrrp-6v32-2p8g

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vrrp-6v32-2p8g

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# Patch Next advisory brief: CVE-2026-70179

Advisory: Microsoft Security Advisory CVE-2026-70179 - ASP.NET Core Elevation of Privilege Vulnerability
IDs: CVE-2026-70179, GHSA-vrrp-6v32-2p8g
Record: https://patchnext.com/advisories/cve-2026-70179 (revision 2, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.aspnetcore.authentication.negotiate 10.0.13, 9.0.21, 8.0.32. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.aspnetcore.authentication.negotiate: affected >= 10.0.0, <= 10.0.12; >= 8.0.0, <= 8.0.31; >= 9.0.0, <= 9.0.20; fixed in 10.0.13, 8.0.32, 9.0.21

## Suggested inspection (read-only)
- NuGet microsoft.aspnetcore.authentication.negotiate: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.aspnetcore.authentication.negotiate.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-vrrp-6v32-2p8g (OSV record GHSA-vrrp-6v32-2p8g lists affected ranges: NuGet microsoft.aspnetcore.authentication.negotiate >=10.0.0 =8.0.0 =9.0.0 <9.0.21 (fixed))
- Verified: https://github.com/advisories/GHSA-vrrp-6v32-2p8g (GitHub-reviewed advisory GHSA-vrrp-6v32-2p8g lists affected ranges: NuGet microsoft.aspnetcore.authentication.negotiate >=10.0.0 =8.0.0 =9.0.0 <=9.0.20)

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