Summary
Impact: Security Feature Bypass. Microsoft rating: Important. Not known to be exploited — Exploitation Less Likely. Customer action: Required.
Details
What kind of security feature could be bypassed by successfully exploiting this vulnerability?
The authentication feature could be bypassed as this vulnerability allows impersonation.
How could an attacker exploit this vulnerability?
An unauthenticated attacker could exploit this vulnerability by sending specially crafted HTTP/2 requests to an affected server. Successful exploitation could allow the attacker to bypass access controls and reach protected resources. No authentication or user interaction is required.
Security updates
18.10.4 — https://learn.microsoft.com/en-us/visualstudio/releases/2026/release-notes
17.14.42 — https://learn.microsoft.com/en-us/visualstudio/releases/2022/release-notes
11.0.0-rc.2 — https://github.com/dotnet/announcements/issues/462
9.0.21 — https://support.microsoft.com/help/5130035
10.0.13 — https://support.microsoft.com/help/5130036
8.0.32 — https://support.microsoft.com/help/5130034
Vulnerabilities 1
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Critical 9.1
ASP.NET Core Security Feature Bypass Vulnerability
Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an unauthorized attacker to bypass a security feature over a network.
Revision history
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#2
Updated the Security Updates table to add KB article links for ASP.NET Core 11.0 and download and KB article links for Microsoft Visual Studio. This is an informational change only; the fixed builds are unchanged.
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#1
Information published.
References
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CVE-2026-70188 ASP.NET Core Security Feature Bypass Vulnerability - HTML
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70188
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Microsoft Exploitability Index
https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1
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Microsoft Support Lifecycle
https://support.microsoft.com/lifecycle
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Common Vulnerability Scoring System
https://www.first.org/cvss