NASM Use-After-Free Vulnerability in Preprocessor Directive Handling

A critical use-after-free vulnerability has been identified in NASM (Netwide Assembler) version 2.17rc0. The issue arises in the 'do_directive' function within 'preproc.c', where the program improperly manages memory by accessing data that has already been freed. This flaw can lead to memory corruption and program crashes. The vulnerability requires local access to exploit and has been publicly disclosed, with an available proof-of-concept exploit.

Impact

Exploitation of this vulnerability causes a heap-use-after-free error, where the program crashes after accessing freed memory. This type of memory corruption can potentially be exploited to execute arbitrary code.

Reproduction

The vulnerability can be reproduced by compiling NASM with AddressSanitizer enabled, and then executing NASM with a specific malformed assembly file that triggers the use-after-free condition. The AddressSanitizer will report the heap-use-after-free error, indicating that the vulnerability has been successfully exploited.