CVE-2026-26171
High CVSS 7.5Published 2026-04-14 ยท last changed 2026-07-15
The fix
Microsoft fixes this in updatesKB5086096, KB5086097. 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 | 8.0.26 | KB5086096 | 2026-09-20 |
| .NET 9.0 installed on Windows | 9.0.15 | KB5086097 | 2026-09-20 |
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
Uncontrolled resource consumption in .NET allows an unauthorized attacker to deny service over a network.
Sources
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H