CVE-2025-27536

Executive Summary

CVE-2025-27536 is a denial-of-service (DoS) vulnerability affecting OpenHarmony versions up to and including v5.0.3. The vulnerability is caused by a type confusion condition that can be triggered by a local attacker. With a CVSS score of 3.3 (Low), the impact is limited to availability, requiring local access and low privileges. No public proof-of-concept (PoC) or exploit code has been identified, and the EPSS score is 0.0%, indicating a very low probability of exploitation in the wild. The vendor has not yet released a patch.

Supply Chain & Package Security

OpenHarmony is an open-source operating system designed for IoT and embedded devices. The vulnerability resides in the core system components, potentially affecting all downstream distributions and devices running the affected versions. Since no patch is available, organizations using OpenHarmony should monitor the official repository for updates and consider implementing additional access controls to mitigate local attack vectors.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
• Base Score: 3.3 (Low)
• Attack Vector: Local (AV:L) – The attacker must have local access to the system.
• Attack Complexity: Low (AC:L) – No special conditions are required to exploit.
• Privileges Required: Low (PR:L) – The attacker needs basic user-level privileges.
• User Interaction: None (UI:N) – No user action is needed.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N) – No data exposure.
• Integrity Impact: None (I:N) – No data modification.
• Availability Impact: Low (A:L) – The system may experience degraded performance or a crash.

Threat Level: Low. The requirement for local access and low privileges reduces the risk, but the lack of a patch means affected systems remain vulnerable.

Deep Dive & Mechanics

The vulnerability is a type confusion (CWE-843) in OpenHarmony's kernel or system service layer. Type confusion occurs when a program uses a variable or object as a different type than intended, leading to memory corruption. In this case, a local attacker can craft a malicious input or system call that causes the operating system to misinterpret a data type, resulting in a crash or hang.

Root Cause Analysis: The exact vulnerable component is not publicly disclosed, but type confusion typically arises in code that handles polymorphic objects or union types without proper validation. For example, a function expecting a pointer to a specific structure might receive a pointer to a different structure, causing out-of-bounds reads or writes.

Attack Vector:

1. The attacker gains local access to the device (e.g., via SSH, ADB, or physical access).
2. The attacker executes a specially crafted program or system call that triggers the type confusion.
3. The operating system enters an undefined state, leading to a denial of service (e.g., kernel panic, service crash, or system hang).

Impact:

• System unavailability until reboot.
• Potential data loss if the crash occurs during write operations.
• No privilege escalation or data theft is possible.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison cannot be provided. However, based on the CWE-843 description, the vulnerable code likely resembles:

// Vulnerable pseudo-code
void process_data(void *data, int type) {
    if (type == 1) {
        struct type_a *a = (struct type_a *)data;
        // Use a->field
    } else if (type == 2) {
        struct type_b *b = (struct type_b *)data;
        // Use b->field
    }
    // Missing type validation
}

A patched version would include strict type checking:

// Patched pseudo-code
void process_data(void *data, int type) {
    if (type == 1 && validate_type_a(data)) {
        struct type_a *a = (struct type_a *)data;
        // Use a->field
    } else if (type == 2 && validate_type_b(data)) {
        struct type_b *b = (struct type_b *)data;
        // Use b->field
    } else {
        // Handle error
    }
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Local access to an OpenHarmony device (v5.0.3 or earlier).
• Low-privilege user account.

Exploitation Steps:

1. Identify the vulnerable system call or interface (e.g., via fuzzing or reverse engineering).
2. Craft a payload that triggers type confusion. Example using a hypothetical ioctl:

#include <fcntl.h>
#include <sys/ioctl.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    int fd = open("/dev/vulnerable_device", O_RDWR);
    if (fd < 0) {
        perror("open");
        return 1;
    }

    // Craft a malicious structure
    struct malicious_payload {
        int type;  // Set to unexpected value
        char data[256];
    } payload;

    payload.type = 0xDEAD;  // Invalid type
    // Fill data with arbitrary values

    if (ioctl(fd, VULN_IOCTL_CMD, &payload) < 0) {
        perror("ioctl");
    }

    close(fd);
    return 0;
}

3. Compile and execute the program on the target device.
4. Observe system crash or hang.

Expected Outcome: The device becomes unresponsive or reboots.

Blue Team (Defensive)

Detection:

• Monitor for unusual system calls or ioctl commands from low-privilege users.
• Use kernel auditing to log type confusion errors.

Mitigation:

• Restrict local access to trusted users only.
• Implement application whitelisting to prevent execution of unknown binaries.
• Apply vendor patches as soon as they become available.

Hunting:

• Search for crash dumps or kernel logs containing type confusion errors.
• Analyze system call patterns for anomalies.

Indicators of Compromise (IOCs)

• System Logs: Kernel panic messages, service crashes, or "type confusion" errors in /var/log/messages or dmesg.
• File Hashes: Unknown or suspicious binaries executed by low-privilege users.
• Network Traffic: None (local vulnerability).
• Process Anomalies: Unexpected processes attempting to access /dev/ or system call interfaces.

Detection Engineering

YARA Rule

rule CVE_2025_27536_TypeConfusion {
    meta:
        description = "Detects potential exploitation of CVE-2025-27536 via type confusion"
        author = "Valters IT"
        date = "2025-03-25"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-27536"
    strings:
        $s1 = "ioctl" ascii wide nocase
        $s2 = "type" ascii wide nocase
        $s3 = "confusion" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: CVE-2025-27536 Type Confusion Exploitation Attempt
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects potential exploitation of CVE-2025-27536 via suspicious ioctl calls
author: Valters IT
date: 2025-03-25
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/exploit'
        CommandLine|contains: 'ioctl'
    condition: selection
falsepositives:
    - Legitimate system administration tools
level: medium

Suricata Rule

alert ip any any -> any any (msg:"CVE-2025-27536 Type Confusion Exploit Attempt"; content:"|69 6f 63 74 6c|"; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Local Access: Limit physical and remote access to OpenHarmony devices to trusted personnel only.
2. Monitor Logs: Enable detailed logging and monitor for crash events or type confusion errors.
3. Apply Patches: Check the OpenHarmony repository (https://gitee.com/openharmony) for updates. Apply patches as soon as they are released.

Long-Term Measures:

1. Code Review: Conduct a thorough review of code handling type conversions and unions.
2. Fuzzing: Implement continuous fuzzing of system call interfaces to identify similar vulnerabilities.
3. Upgrade: Plan to upgrade to a patched version once available.

Workarounds:

• Disable unnecessary system services that may expose the vulnerable interface.
• Use mandatory access controls (e.g., SELinux) to restrict process capabilities.

Valters IT
Securing Digital Frontiers