CVE-2026-47300: Microsoft Security Advisory CVE-2026-47300 – .NET Elevation of Privilege Vulnerability

Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core Negotiate Authentication (Microsoft.AspNetCore.Authentication.Negotiate). This advisory also p…

8.8CVSS Score

HIGHSeverity

NOCISA KEV

0.5%EPSS Score

VulnerabilityImpact Type

📋 Vulnerability Details

CVE ID	CVE-2026-47300
Vendor	nuget
Affected Product	Microsoft.AspNetCore.Authentication.Negotiate
Vulnerability Type	Vulnerability
CVSS Score	8.8 (HIGH)
EPSS Score	0.5% probability of exploitation in the next 30 days
Actively Exploited	❌ No known exploitation
Patch Status	See Vendor Advisory →
Reported By	CYBERDUDEBIVASH SENTINEL APEX Intelligence (via github_advisories)

🔬 Technical Analysis

Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in ASP.NET Core Negotiate Authentication (Microsoft.AspNetCore.Authentication.Negotiate). This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. An elevation of privilege vulnerability exists in the ASP.NET Core Negotiate authentication handler in .NET 8, .NET 9, and .NET 10 due to improper validation.

Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/TBD

CVSS Details - Version: 3.1

• Severity: High

• Score: 8.8

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

• Weakness: CWE-303 (Incorrect Implementation of Authentication

🎯 Known Indicators of Compromise

{"type":"url","value":"https://github.com/dotnet/announcements/issues/**TBD**","confidence_score":0.82,"first_seen":"2026-07-21","source_count":1} {"type":"domain","value":"asp.net","confidence_score":0.75,"first_seen":"2026-07-21","source_count":1}

📚 Advisory References

⚡ DETECTION RULES AVAILABLE

Get CVE-2026-47300 Detection Pack

Sigma rules, YARA signatures, IOC table, and SIEM queries for Splunk, Elastic, Sentinel, and Chronicle — deployable in 5 minutes.

✓ Sigma Rules ✓ YARA Pack ✓ IOC Table ✓ SIEM Queries

🛡️ Get Detection Pack → 🔌 Access via API →