CVE-2025-27242

Executive Summary

CVE-2025-27242 is a denial-of-service (DoS) vulnerability in OpenHarmony v5.0.3 and prior versions. The flaw allows a local attacker to cause a denial of service through improper input validation. With a CVSS score of 3.3 (Low), this vulnerability requires local access and low privileges to exploit. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild. No public proof-of-concept (PoC) or exploit code is currently available. The vulnerability is classified under CWE-20 (Improper Input Validation) and aligns with MITRE ATT&CK tactic T1499 (Endpoint Denial of Service).

Supply Chain & Package Security

OpenHarmony is an open-source operating system for IoT and embedded devices. The vulnerability affects the core OS kernel or a system service, not a specific package manager (NPM, PyPI, Go, Ruby). Therefore, supply chain package security is not directly applicable. However, organizations using OpenHarmony in their products should verify the integrity of their OS images and ensure they are sourced from trusted repositories.

CVSS Breakdown & Threat Level

• CVSS Score: 3.3 (Low)
• Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
• Attack Vector (AV): Local (L) – The attacker must have physical or logical access to the system.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): Low (L) – The attacker needs basic user-level privileges.
• User Interaction (UI): None (N) – No user action is required.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): Low (L) – The attack can cause a denial of service, but the impact is limited.

Threat Level: Low. The requirement for local access and low privileges reduces the risk. However, in multi-tenant or IoT environments, a local attacker could disrupt services.

Deep Dive & Mechanics

The vulnerability stems from improper input validation in OpenHarmony v5.0.3 and earlier. A local attacker can craft a malicious input that, when processed by a system component (likely a kernel module or system service), causes the system to crash or become unresponsive. The exact component is not disclosed, but based on the CWE-20 classification, the issue involves insufficient sanitization of user-supplied data.

Attack Scenario:

1. An attacker gains local access to an OpenHarmony device (e.g., via a compromised app or physical access).
2. The attacker sends a specially crafted input to a vulnerable system call or service.
3. The input triggers a buffer overflow, infinite loop, or resource exhaustion, leading to a denial of service.

Root Cause: The software does not properly validate the length, format, or content of input data, allowing an attacker to cause unexpected behavior.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is unknown. However, based on the CWE-20 classification, the vulnerable code likely resembles:

// Vulnerable code (hypothetical)
void process_input(char *input) {
    char buffer[256];
    strcpy(buffer, input); // No bounds checking
    // ... further processing
}

A patched version would include input validation:

// Patched code (hypothetical)
void process_input(char *input) {
    char buffer[256];
    if (strlen(input) >= sizeof(buffer)) {
        // Handle error
        return;
    }
    strcpy(buffer, input);
    // ... further processing
}

Exploitation & Lab Setup

Red Team

Objective: Simulate a local DoS attack on OpenHarmony v5.0.3.

Prerequisites:

• OpenHarmony v5.0.3 device or emulator.
• Local user access (e.g., via ADB or SSH).

Steps:

1. Identify the vulnerable service or system call (requires reverse engineering or fuzzing).
2. Craft a malicious input that triggers the DoS.
3. Execute the exploit:

# Example: Send a malformed input to a vulnerable service
echo -n -e '\x00\x01\x02...' > /proc/vulnerable_device

Expected Outcome: The system becomes unresponsive or crashes.

Blue Team

Objective: Detect and mitigate exploitation attempts.

Detection:

• Monitor for unusual system crashes or reboots.
• Use system call auditing to detect anomalous inputs.

Mitigation:

• Restrict local user privileges.
• Apply input validation at the application layer.
• Monitor logs for patterns of repeated crashes.

Indicators of Compromise (IOCs)

• System Logs: Repeated crash logs in /var/log/syslog or dmesg.
• Process Behavior: Unexpected termination of system services.
• Network Traffic: None (local attack).
• File System: Presence of unusual files in /tmp or /proc.

Example IOC (Syslog):

kernel: [12345.678] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000

Detection Engineering

YARA Rule

rule CVE_2025_27242_OpenHarmony_DoS {
    meta:
        description = "Detects potential exploitation of CVE-2025-27242"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-27242"
    strings:
        $s1 = "OpenHarmony" nocase
        $s2 = "v5.0.3" nocase
        $s3 = "improper input" nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-27242 OpenHarmony DoS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2025-27242 via system crash logs
author: Valters IT
date: 2025-04-10
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "kernel: BUG: unable to handle kernel NULL pointer dereference"
        - "kernel: Oops:"
        - "kernel: general protection fault"
    condition: selection
falsepositives:
    - Legitimate kernel bugs
level: medium

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-27242 OpenHarmony DoS Attempt"; content:"OpenHarmony"; nocase; content:"v5.0.3"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Local Access: Limit user privileges to prevent exploitation.
2. Monitor Systems: Watch for unusual crashes or resource exhaustion.
3. Apply Workarounds: If possible, disable the vulnerable service or component.

Long-Term Fix:

• Await an official patch from OpenHarmony. Once available, apply it immediately.
• Implement input validation in custom applications running on OpenHarmony.

Vendor Contact: OpenHarmony security team (security@openharmony.io).

Valters IT