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CVE-2026-70179 high CVSS 7.5

Vulnerability in Microsoft.AspNetCore.Authentication.Negotiate (CVE-2026-70179)

Summary

Vulnerability in Microsoft.AspNetCore.Authentication.Negotiate (CVE-2026-70179). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 9.0.21 or later.

Original description

The description as published by the source.

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

Affected Packages

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]…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-70179 has been found in Microsoft.AspNetCore.Authentication.Negotiate.
Successful exploitation can lead to full system takeover. CVSS score: 7.5/10.
What to do: upgrade Microsoft.AspNetCore.Authentication.Negotiate to 9.0.21 or later.
If unsure, ask your IT team or search "Microsoft.AspNetCore.Authentication.Negotiate CVE-2026-70179" on the vendor's site.

CVE-2026-70179 (Microsoft.AspNetCore.Authentication.Negotiate) — CWE-290 / CVSS v3 7.5
Attack vector: remote (network-reachable) / no user interaction
Patched: 9.0.21 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-290) exists in Microsoft.AspNetCore.Authentication.Negotiate.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.AspNetCore.Authentication.Negotiate.

🔥 Severity

Severity: High (CVSS 7.5/10). Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 9.0.21.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Microsoft.AspNetCore.Authentication.Negotiate' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Microsoft.AspNetCore.Authentication.Negotiate' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Microsoft.AspNetCore.Authentication.Negotiate を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade Microsoft.AspNetCore.Authentication.Negotiate to 9.0.21

    ステージング環境で 9.0.21 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

nuget Microsoft.AspNetCore.Authentication.Negotiate
[{"type":"ECOSYSTEM","events":[{"introduced":"9.0.0"},{"fixed":"9.0.21"}]}]

References

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