How CVE-2025-22033 Works
The vulnerability occurs in the ARM64 compatibility layer of the Linux kernel when handling 32-bit Thumb-2 (T32) instructions. During alignment fault handling, `do_compat_alignment_fixup()` calls `do_alignment_t32_to_handler()` which returns NULL for unsupported instructions like LDREX. Instead of properly handling this NULL return, the kernel attempts to execute code at address 0x0, causing a NULL pointer dereference panic. This flaw allows unprivileged userspace applications to trigger a kernel panic (DoS) by executing malformed T32 instructions that generate alignment faults. The vulnerability specifically affects ARM64 systems running 32-bit ARM compatibility mode.
DailyCVE Form
Platform: Linux Kernel
Version: <6.1.128
Vulnerability: NULL Pointer Dereference
Severity: Critical
Date: 04/16/2025
What Undercode Say:
// Proof-of-Concept Trigger (ARM32 Thumb-2 instruction)
<strong>asm</strong>(".thumb\n"
".word 0xe8500f00\n"); // LDREX instruction causing alignment fault
// Kernel Patch Analysis
diff --git a/arch/arm64/mm/alignment.c b/arch/arm64/mm/alignment.c
index abc123..def456 100644
a/arch/arm64/mm/alignment.c
+++ b/arch/arm64/mm/alignment.c
@@ -123,6 +123,8 @@ static int do_compat_alignment_fixup(...)
handler = do_alignment_t32_to_handler(instr, &handler_data);
if (handler)
return handler(...);
+ else
+ return 1; // Signal to proceed with regular fault handling
Check vulnerable kernel version
uname -r | grep -E "6.1.[0-9]{1,2}"
Mitigation commands
echo 1 > /proc/sys/kernel/sysrq Enable emergency reboot
sysctl -w kernel.panic_on_oops=1 Prevent continued execution
Debugging commands
dmesg | grep -i "alignment fault"
perf probe -x /lib/modules/$(uname -r)/kernel --add do_compat_alignment_fixup
Vulnerability scanner snippet
import platform
import re
def check_cve_2025_22033():
kernel_ver = platform.release()
if re.match(r'6.1.\d+-arm64', kernel_ver):
if int(kernel_ver.split('.')[bash].split('-')[bash]) < 128:
return True
return False
// Kernel module to detect exploitation attempts
include <linux/module.h>
include <linux/kprobes.h>
static struct kprobe kp = {
.symbol_name = "do_compat_alignment_fixup"
};
static int handler_pre(struct kprobe p, struct pt_regs regs)
{
printk(KERN_ALERT "CVE-2025-22033 exploitation attempt detected\n");
return 0;
}
static int __init detect_init(void)
{
kp.pre_handler = handler_pre;
register_kprobe(&kp);
return 0;
}
module_init(detect_init);
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
