CVE-2026-88092: ASP.NET Core Tampering Vulnerability

Severity: critical (CVSS 9.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.9% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-31
Weakness: CWE-444

Description

Inconsistent interpretation of http requests ('http request/response smuggling') in ASP.NET Core allows an unauthorized attacker to perform tampering over a network.

Affected products

Microsoft .NET Core: from 8.0.0 before 8.0.32; from 9.0.0 before 9.0.21; from 10.0.0 before 10.0.13; from 11.0.0 (excl.); 11.0-rc1 — fixed in 10.0.13, 8.0.32, 9.0.21
Microsoft Visual Studio 2022 version 17.14: from 17.14.0 before 17.14.42 — fixed in 17.14.42
Microsoft Visual Studio 2026 version 18.9: from 18.10.0 before 18.10.4 — fixed in 18.10.4
Microsoft ASP.NET Core 10.0: from 10.0 before 10.0.13 — fixed in 10.0.13
Microsoft ASP.NET Core 11.0: from 11.0 before 11.0.0-rc.2 — fixed in 11.0.0-rc.2
Microsoft ASP.NET Core 8.0: from 8.0 before 8.0.32 — fixed in 8.0.32
Microsoft ASP.NET Core 9.0: from 9.0 before 9.0.21 — fixed in 9.0.21
Microsoft Visual Studio 2026 version 18.10: from 18.10.0 before 18.10.4 — fixed in 18.10.4
Microsoft Visual Studio 2022 version 17.14: from 17.14.0 before 17.14.42 — fixed in 17.14.42

How to fix

Upgrade to a fixed version: Microsoft .NET Core 10.0.13, 8.0.32, 9.0.21; Microsoft Visual Studio 2022 version 17.14 17.14.42; Microsoft Visual Studio 2026 version 18.9 18.10.4; Microsoft ASP.NET Core 10.0 10.0.13; Microsoft ASP.NET Core 11.0 11.0.0-rc.2; Microsoft ASP.NET Core 8.0 8.0.32; Microsoft ASP.NET Core 9.0 9.0.21; Microsoft Visual Studio 2026 version 18.10 18.10.4; Microsoft Visual Studio 2022 version 17.14 17.14.42. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-88092

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