| Package | Affected versions | Patched versions |
|---|---|---|
| Microsoft.AspNetCore.Authentication.Negotiate | ≥ 10.0.0, < 10.0.13≥ 8.0.0, < 8.0.32≥ 9.0.0, < 9.0.21 | 10.0.138.0.329.0.21 |
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 for this issue can be found at https://github.com/dotnet/announcements/issues/458
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)
The vulnerability affects Microsoft .NET projects that use an affected package version listed below.
| Package name | Affected version | Patched version |
|---|---|---|
| Microsoft.AspNetCore.Authentication.Negotiate | >= 10.0.0, <= 10.0.12 | 10.0.13 |
| Microsoft.AspNetCore.Authentication.Negotiate | >= 8.0.0, <= 8.0.31 | 8.0.32 |
| Microsoft.AspNetCore.Authentication.Negotiate | >= 9.0.0, <= 9.0.20 | 9.0.21 |
If using a package listed in affected packages, you're exposed to the vulnerability.
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site freedotnet --info command.Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.
Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.
If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.
Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.
You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.
The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
V1.0 (10/13/2026): Advisory published.