Diffing Binary Patches

A security patch is a description of a vulnerability written in the vendor's own code. Diffing the binary before and after the fix turns a one-line advisory into the exact function, the exact check that was added, and — reasoning backward — the input that reached the bug before the patch. This is the core of 1-day analysis: the fix tells you where to look, the diff tells you what, and the pre-patch reachability tells you how.

When to Use

• Comparing two versions of the same binary (DLL, ELF, driver) to find what a security update changed
• Turning a CVE advisory or Patch-Tuesday bulletin into the specific vulnerable code
• Extracting a Microsoft patch (MSU/MSP/cab, delta-compressed) into a full binary you can diff
• Assessing whether a "silent" fix in a new release closed a security bug