Four vulnerabilities fixed, including two critical ones

The updates published by Microsoft in October 2026 target four distinct flaws in recent .NET versions. The most critical, CVE-2026-111497, exploits a buffer overflow in the Brotli decompression algorithm integrated into .NET. According to Microsoft’s official blog, this flaw allows an unauthenticated attacker to read or corrupt process memory, paving the way for information leaks, denial-of-service attacks, or privilege escalations. A second flaw, CVE-2026-114148, affects the property metadata of .NET 10 and 11 Linux tarballs, as well as ASP.NET Core distributions for .NET 8 and 9. It could allow a local attacker to modify files and gain elevated rights on the system.

A memory overflow flaw in Brotli could allow an unauthenticated attacker to corrupt data or escalate privileges on a vulnerable system.

Which systems and applications are affected?

The fixes specifically concern applications using Brotli decompression features via ASP.NET Core, automated HTTP requests with HttpClient, or System.IO.Compression APIs. For users of .NET 11 in Release Candidate 2, Microsoft recommends migrating to RC3 to access the patches. Framework-dependent applications require a runtime update, while self-contained versions must be recompiled and republished. Users of ASP.NET Core tarballs under .NET 8 and 9 must download a new runtime version, available since October 19, 2026.

What this means here: risks for critical infrastructures and local developers

In Benin and West Africa, where public and private digital infrastructures often rely on diverse technological stacks, these vulnerabilities could impact administrations using .NET frameworks for online services or internal applications. For example, a government website or a banking platform integrating ASP.NET Core would be exposed to denial-of-service attacks or leaks of sensitive data if patches are not applied. Local developers working on projects using Brotli for data compression, particularly in cloud environments or mobile applications, should prioritize these updates to avoid breaches. Companies using Linux distributions of .NET may also see their systems vulnerable to local attacks aimed at escalating privileges, a risk especially sensitive in environments where root access is shared.

Other included fixes: corrupted memory and Blazor debugger

The updates also include fixes for two additional vulnerabilities: CVE-2026-70197, a memory corruption issue in SocketAsyncEventArgs affecting all versions of .NET 8 through 11, and CVE-2026-102870, a flaw in the Blazor WebAssembly debugger, limited to .NET 10 and 11. Though less publicized, these vulnerabilities could, if exploited, lead to critical instabilities in real-time applications or systems requiring reliable execution.

Official recommendation: update immediately

Microsoft emphasizes the urgency of these patches. In a statement signed by Rahul Bhandari, Microsoft’s security lead, the company states: « We recommend updating as soon as possible. » This urgency stems from the potential for remote exploitation of certain vulnerabilities, particularly the one linked to Brotli, which requires no prior authentication. For organizations, this means scheduling maintenance windows to apply these fixes without disrupting production services, while also reviewing dependencies of critical applications.