CWE-622, Improper Validation of Function Hook Arguments, applies when a product hooks user-accessible API functions without checking the arguments. It matters most for privileged defensive software such as antivirus tools and firewalls that hook kernel calls.
How it happens
A hook sits in front of a function and sees every call. The hook author often assumes callers pass well-formed arguments, because the original function would have handled bad ones. But the hook runs first, and it may run with high privileges. A caller who passes a wrong type, a bad pointer or an out-of-range value can crash the hook, bypass the protection it provides or attack the product itself.
MITRE's observed examples include denial of service in a firewall using standard Microsoft functions, a function that did not check its argument type and allowed an arbitrary memory write (CVE-2007-1376), and invalid syscall arguments that bypassed code execution limits.
What an attacker gains
The record lists an integrity impact: unexpected state. In the examples, that meant service disruption, memory writes and bypassed restrictions.
How to find it
The record lists no detection methods. Review each hooked function and compare the checks the hook performs against what the original API defines. Fuzzing the hooked calls with malformed arguments is a practical way to test them.
How to fix it
- Verify all arguments, as defined by the API you are protecting.
- Drop privileges before invoking such functions, if possible.
Quick check
Why are hooks in security products a special risk?
They often run with elevated privileges, so a bad argument can bypass the protection or attack the product itself.
