Title: NetBSD semop Arbitrary Code Execution Vulnerability
Severity: HIGH
Description:
An input validation error exists in the NetBSD kernel that may result in a denial of service or the user execution of arbitrary code with elevated privileges.
The problem is due to insufficient length checking on a parameter passed to the semop() function, which acts as the entry point for the semop syscall. The function stores an unsigned integer argument 'nsops' in a local signed variable. This value is then used to copy data from user memory onto the process' kernel stack. The vulnerability exists because it is possible to bypass the check used to ensure that a sane value is given. This can be be accomplished by passing a large numeric value and causing a signed integer overflow.
This vulnerability can be used to write an almost arbitrary number of bytes to the process' kernel stack. It could be exploited to cause a kernel trap, call arbitrary kernel code, or execute arbitrary code on an architecture where stack memory is executable.
Affected Products:
- NetBSD NetBSD 1.4.0
- NetBSD NetBSD 1.4.1
- NetBSD NetBSD 1.4.2
- NetBSD NetBSD 1.4.3
- NetBSD NetBSD 1.5.0
- NetBSD NetBSD 1.5.1
- NetBSD NetBSD current pre20010805
References:
- NetBSD: NetBSD Security Page
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