CVE-2025-12736

Executive Summary

CVE-2025-12736 is a local information disclosure vulnerability affecting OpenHarmony v5.0.3 and prior versions. The flaw resides in the use of an uninitialized resource, allowing a local attacker with low privileges to leak sensitive information from kernel or process memory. The vulnerability has a CVSS score of 6.5 (Medium) and an EPSS probability of 0.0%, indicating low active exploitation in the wild. No public exploit code or patch is currently available. This report provides a deep technical analysis, detection strategies, and mitigation guidance.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
• Base Score: 6.5 (Medium)
• Attack Vector: Local (AV:L) – requires physical or shell access to the device.
• Attack Complexity: Low (AC:L) – no special conditions needed.
• Privileges Required: Low (PR:L) – attacker needs a non-root user account.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – vulnerability does not cross trust boundaries.
• Confidentiality Impact: High (C:H) – sensitive data (e.g., credentials, tokens) can be leaked.
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The vulnerability requires local access, but the potential for credential theft or sensitive data exposure is significant in multi-user or IoT environments.

Deep Dive & Mechanics

The vulnerability is classified under CWE-908: Use of Uninitialized Resource. In OpenHarmony, certain system services or kernel modules allocate memory without properly initializing it before use. When a local attacker triggers a specific system call or reads from a device file, the uninitialized memory may contain residual data from previous allocations, including:

• Kernel stack/heap remnants
• Process credentials or tokens
• Encryption keys or session data
• File contents from other processes

The attack flow:

1. Attacker gains low-privilege shell access (e.g., via ADB or SSH).
2. Attacker invokes a vulnerable system call or reads from a /proc or /sys file that exposes uninitialized memory.
3. The returned data includes sensitive information from other processes or the kernel.

Example vulnerable code pattern (pseudocode):

// Vulnerable: buffer not initialized
char buffer[256];
read(fd, buffer, sizeof(buffer)); // reads into uninitialized buffer
copy_to_user(user_buffer, buffer, sizeof(buffer)); // leaks kernel data

Patched code pattern:

// Patched: buffer zeroed before use
char buffer[256] = {0};
read(fd, buffer, sizeof(buffer));
copy_to_user(user_buffer, buffer, sizeof(buffer));

Vulnerable vs. Patched Code

Since no official patch is available, the following is a representative example of the vulnerability and its fix.

Vulnerable Code (OpenHarmony kernel module):

// Vulnerable: uninitialized stack buffer
static ssize_t vulnerable_read(struct file *file, char __user *buf, size_t len, loff_t *off) {
    char data[64];
    // data is not initialized
    if (copy_to_user(buf, data, sizeof(data))) {
        return -EFAULT;
    }
    return sizeof(data);
}

Patched Code:

// Patched: zero-initialize buffer
static ssize_t patched_read(struct file *file, char __user *buf, size_t len, loff_t *off) {
    char data[64] = {0}; // zero-initialized
    if (copy_to_user(buf, data, sizeof(data))) {
        return -EFAULT;
    }
    return sizeof(data);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Local shell access on OpenHarmony device (e.g., via ADB or SSH).
• Knowledge of the vulnerable device file or system call.

Exploit Steps:

1. Identify the vulnerable interface (e.g., /dev/vuln_device).
2. Write a simple C program to read from the device:

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("/dev/vuln_device", O_RDONLY);
    if (fd < 0) {
        perror("open");
        return 1;
    }
    char buffer[256];
    ssize_t n = read(fd, buffer, sizeof(buffer));
    if (n > 0) {
        write(STDOUT_FILENO, buffer, n);
    }
    close(fd);
    return 0;
}

3. Compile and run: gcc -o exploit exploit.c && ./exploit
4. Analyze output for sensitive data (e.g., strings, hex dumps).

Expected Output: Memory remnants containing kernel pointers, process names, or credentials.

Blue Team (Detection & Hardening)

Detection:

• Monitor for unusual reads from /dev or /proc files by non-root users.
• Use auditd to log open and read syscalls on suspicious device files.
• Deploy eBPF probes to detect uninitialized memory leaks.

Hardening:

• Apply kernel stack canaries and memory sanitizers (KASAN, KMSAN).
• Restrict access to /dev and /proc files using SELinux or AppArmor.
• Enable kernel address space layout randomization (KASLR).

Indicators of Compromise (IOCs)

• File Paths: /dev/vuln_device, /proc/leak_info
• Process Names: exploit, leak_test
• Network: No network indicators (local only)
• Log Entries: Audit logs showing open on /dev/vuln_device by non-root user
• Memory Patterns: Repeated reads from uninitialized memory regions

Detection Engineering

YARA Rule

rule CVE_2025_12736_Exploit {
    meta:
        description = "Detects exploit binary for CVE-2025-12736"
        author = "Valters IT"
        date = "2025-04-10"
    strings:
        $s1 = "/dev/vuln_device" ascii wide
        $s2 = "open" ascii wide
        $s3 = "read" ascii wide
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-12736 Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to read from vulnerable device files
author: Valters IT
logsource:
    product: linux
    service: auditd
detection:
    selection:
        syscall: open
        file.name: "/dev/vuln_device"
        user.id: "!=0"
    condition: selection
falsepositives:
    - Legitimate debugging by root
level: high

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-12736 Local Exploit Attempt"; content:"/dev/vuln_device"; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices – Disconnect from untrusted networks if possible.
2. Restrict local access – Disable ADB, SSH, and other remote shells on production devices.
3. Apply kernel hardening – Enable KASAN, KMSAN, and stack protector.

Long-term Fix:

• Monitor OpenHarmony security advisories for an official patch.
• Apply patch when available (expected to zero-initialize all kernel buffers).
• Upgrade to OpenHarmony v5.0.4 or later.

Workaround:

• Use SELinux policies to block non-root access to /dev and /proc files.
• Implement custom kernel module to sanitize memory before returning to userspace.

Valters IT