CVE-2026-26127: .NET Denial of Service Vulnerability

March 11, 2026 (updated March 12, 2026)

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 9.0 and .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A denial of service vulnerability exists in .NET and Microsoft.Bcl.Memory due to an out-of-bounds read when decoding malformed Base64Url input.

References

github.com/advisories/GHSA-73j8-2gch-69rq
github.com/dotnet/runtime
github.com/dotnet/runtime/security/advisories/GHSA-73j8-2gch-69rq
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26127
nvd.nist.gov/vuln/detail/CVE-2026-26127

Code Behaviors & Features

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