CVE-2026-111497
UnratedPublished 2026-10-22 ยท last changed 2026-10-24
The fix
Microsoft fixes this in updatesKB5133966, KB5133964, KB5133965. 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 10.0 installed on Windows | 10.0.403 | KB5133966 | 2026-10-25 |
| .NET 11.0 installed on Windows | 11.0.100-rc.3.26522.148 | configuration change | 2026-10-25 |
| .NET 8.0 installed on Windows | 8.0.427 | KB5133964 | 2026-10-25 |
| .NET 9.0 installed on Windows | 9.0.320 | KB5133965 | 2026-10-25 |
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
A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream. Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.