CVE-2025-27131

Executive Summary

CVE-2025-27131 is a denial-of-service (DoS) vulnerability in OpenHarmony v5.0.3 and prior versions. The flaw allows a local attacker to cause a system crash or resource exhaustion through improper input validation. With a CVSS score of 6.1 (Medium), the vulnerability requires local access and low privileges, making it a risk in multi-user or IoT environments where untrusted users have local shell access. No public exploit code or proof-of-concept is currently available, and the vendor has not released a patch.

Supply Chain & Package Security

OpenHarmony is an open-source operating system for IoT and embedded devices. The vulnerability exists in the core OS kernel or system service layer, not in a specific package manager (NPM, PyPI, Go, Ruby). However, organizations using OpenHarmony in their supply chain should assess exposure and apply mitigations.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Local (L) – attacker must have local access.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): Low (L) – attacker needs basic user privileges.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – impact confined to the vulnerable component.
• Confidentiality (C): None (N) – no data exposure.
• Integrity (I): None (N) – no data modification.
• Availability (A): High (H) – system crash or resource exhaustion.

Threat Level: Medium. The vulnerability is not remotely exploitable and requires local access, but it can cause significant service disruption in shared or IoT environments.

Deep Dive & Mechanics

The vulnerability stems from improper input validation in a system service or kernel component of OpenHarmony. When a local attacker sends a specially crafted input (e.g., malformed IPC message, invalid system call argument, or oversized data), the component fails to sanitize the input, leading to a buffer overflow, infinite loop, or resource exhaustion. This results in a denial-of-service condition, potentially crashing the entire system or making it unresponsive.

Root Cause: Lack of bounds checking or input validation in the affected function. The component trusts user-supplied data without verifying its size or format, allowing an attacker to trigger undefined behavior.

Attack Vector: Local user with low privileges executes a malicious binary or script that interacts with the vulnerable service.

Vulnerable vs. Patched Code

Since no patch is available, the following is a hypothetical comparison based on typical input validation fixes.

Vulnerable Code (C pseudocode):

void process_input(char *user_input) {
    char buffer[256];
    strcpy(buffer, user_input); // No bounds check
    // Process buffer...
}

Patched Code (C pseudocode):

void process_input(char *user_input) {
    char buffer[256];
    if (strlen(user_input) >= sizeof(buffer)) {
        return -1; // Reject oversized input
    }
    strcpy(buffer, user_input);
    // Process buffer...
}

Exploitation & Lab Setup

Red Team (Exploitation)

No public exploit code exists. However, a local attacker could craft a proof-of-concept as follows:

1. Identify the vulnerable service: Use ps or ls /proc to find system processes.
2. Craft malicious input: Create a binary that sends an oversized or malformed IPC message to the target service.
3. Trigger the vulnerability: Execute the binary as a low-privileged user.

Example PoC (Python):

import socket
import struct

# Assume vulnerable service listens on a Unix socket
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.connect("/var/run/vuln_service.sock")
payload = b"A" * 4096  # Oversized input
sock.send(payload)
sock.close()

Blue Team (Detection & Hardening)

• Monitor system logs: Look for crashes, segmentation faults, or service restarts.
• Restrict local access: Use mandatory access controls (e.g., SELinux, AppArmor) to limit user capabilities.
• Apply resource limits: Use ulimit to restrict memory and file descriptor usage per user.
• Enable kernel hardening: Use sysctl to enable ASLR, stack canaries, and other protections.

Indicators of Compromise (IOCs)

• System logs: Kernel panics, OOM killer messages, or service crashes in /var/log/messages or dmesg.
• Process anomalies: Unexpected high CPU or memory usage by a low-privilege user process.
• File artifacts: Malicious binaries or scripts in /tmp or user home directories.
• Network indicators: Unusual IPC traffic on local sockets (e.g., Unix domain sockets).

Detection Engineering

YARA Rule

rule CVE_2025_27131_OpenHarmony_DoS {
    meta:
        description = "Detects potential exploit attempts for CVE-2025-27131"
        author = "Valters IT"
        date = "2025-03-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-27131"
    strings:
        $s1 = "OpenHarmony" nocase
        $s2 = "process_input" nocase
        $s3 = "buffer overflow" nocase
    condition:
        any of ($s*) and filesize < 10MB
}

Sigma Rule

title: CVE-2025-27131 OpenHarmony DoS Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects local DoS attempts against OpenHarmony
author: Valters IT
logsource:
    product: linux
    service: syslog
detection:
    selection:
        - "kernel: BUG: unable to handle kernel paging request"
        - "kernel: segfault at"
        - "kernel: OOM killer"
    condition: selection
falsepositives:
    - Legitimate kernel bugs
level: high

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-27131 OpenHarmony DoS Attempt"; content:"|41 41 41 41|"; depth:100; reference:cve,2025-27131; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: Restrict local user access to the vulnerable system. Use chmod and chown to limit executable permissions.
• Short-term: Monitor for vendor patches. Subscribe to OpenHarmony security advisories.
• Long-term: Implement input validation in custom applications. Use fuzzing tools to identify similar vulnerabilities.
• Workaround: If the vulnerable service is not critical, disable it via systemd or init scripts.

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