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Advisory 2007-02-01.01

Comodo Multiple insufficient argument validation of hooked SSDT function Vulnerability

Basic information:

Release date: February 01, 2007

Last update: February 07, 2007


Character:System crash


Testing program:


Hooking SSDT functions requires extra caution. SSDT function handlers are executed in the kernel mode but their callers are executed in the user mode. Hence all function arguments come from the user mode. This is why it is necessary to validate these arguments properly. Otherwise a simple user call can easily crash the whole system. This bug usually results in a system crash. However, it may happen that this bug is even more dangerous and may lead to the execution of an arbitrary code in the privileged kernel mode.

Comodo Firewall Pro (former Comodo Personal Firewall) hooks many functions in SSDT and in at least seven cases it fails to validate arguments that come from the user mode. User calls to NtConnectPort (CFP is not affected), NtCreatePort (CFP is not affected), NtCreateSection, NtOpenProcess, NtOpenSection, NtOpenThread and NtSetValueKey with invalid argument values can cause system crashes because of errors in CFP driver cmdmon.sys. Further impacts of this bug (like arbitrary code execution in the kernel mode) were not examined.

Vulnerable software:

Not vulnerable software: