Great analysis by NCC Group on CVE-2026-21236, a heap-based buffer overflow in the AFD.sys kernel driver

This blog post presents a patch diff, vulnerability analysis, and proof-of-concept generation of CVE-2026-21236 - a heap-based buffer overflow in afd.sys, the kernel-mode driver underpinning Windows socket operations.

Patched by Microsoft on February 11, 2026, the vulnerability resides in the SAN connect handling path and carries an Elevation of Privilege impact, allowing a local attacker to corrupt kernel pool memory. The paper is presented from her point of view. We will also include a small section on AI, applied to patch diffing.

#reverse #windows