CVE-2026-62899: Microsoft Security Advisory CVE-2026-62899 – .NET Security Feature Bypass Vulnerability

August 11, 2026

Microsoft is releasing this security advisory to provide information about a vulnerability in System.Net.HttpListener. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

Inconsistent interpretation of http requests (‘http request/response smuggling’) in .NET allows an unauthorized attacker to bypass a security feature over a network.

References

github.com/advisories/GHSA-r6mh-95jw-g7qg
github.com/dotnet/announcements/issues/427
github.com/dotnet/runtime/security/advisories/GHSA-r6mh-95jw-g7qg
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62899
nvd.nist.gov/vuln/detail/CVE-2026-62899

Code Behaviors & Features

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