CVE-2025-26646
High CVSS 8Published 2025-05-13 ยท last changed 2026-06-17
The fix
Microsoft fixes this in updatesKB5059200, KB5059201. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| .NET 8.0 installed on Windows | 8.0.16 | KB5059200 | 2026-09-16 |
| .NET 9.0 installed on Windows | 9.0.5 | KB5059201 | 2026-09-16 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
External control of file name or path in .NET, Visual Studio, and Build Tools for Visual Studio allows an authorized attacker to perform spoofing over a network.
Sources
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H