CVE-2024-24198

Executive Summary

CVE-2024-24198 is a security advisory affecting the SmartDNS project, specifically in commit 54b4dc. The vulnerability is described as a misaligned address issue discovered in the file smartdns/src/util.c. This type of flaw typically arises from improper memory alignment, which can lead to undefined behavior, crashes, or potentially exploitable conditions such as information disclosure or denial of service. The CVSS score is 0.0, indicating that no official CVSS vector has been assigned, and the EPSS score is 0.0%, suggesting no active exploitation in the wild. No public proof-of-concept (PoC) code, exploit database entries, or patch details are currently available. The vendor status is unknown, and no official patch has been released.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Unassigned)
• CVSS Vector: UNKNOWN
• Attack Vector (AV): UNKNOWN
• Attack Complexity (AC): UNKNOWN
• Privileges Required (PR): UNKNOWN
• User Interaction (UI): UNKNOWN
• Scope (S): UNKNOWN
• Confidentiality (C): UNKNOWN
• Integrity (I): UNKNOWN
• Availability (A): UNKNOWN
• EPSS Score: 0.0% (Very low probability of exploitation)
• Threat Level: Low (based on lack of exploitation and public PoC)

Deep Dive & Mechanics

The vulnerability is located in the smartdns/src/util.c file at commit 54b4dc. A misaligned address occurs when a pointer or memory access is not aligned to the natural boundary required by the data type (e.g., a 4-byte integer accessed at an odd address). In C/C++, this can cause undefined behavior, including:

• SIGBUS (Bus error) on architectures that require strict alignment (e.g., ARM, SPARC).
• Performance degradation on x86 (which handles misalignment in hardware but with a penalty).
• Potential security implications if the misalignment leads to reading or writing unintended memory regions, possibly leaking sensitive data or corrupting adjacent structures.

The specific code path in util.c likely involves pointer arithmetic or casting that results in an unaligned access. Without a patch or detailed analysis, the exact impact is speculative, but it could be triggered by crafted DNS queries or configuration inputs.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code resides in smartdns/src/util.c at commit 54b4dc. A hypothetical fix would involve ensuring proper alignment, for example by using memcpy to safely copy unaligned data or by aligning buffers.

Vulnerable (hypothetical):

// Vulnerable: Direct dereference of potentially unaligned pointer
uint32_t value = *(uint32_t*)(buffer + offset);

Patched (hypothetical):

// Patched: Safe copy using memcpy
uint32_t value;
memcpy(&value, buffer + offset, sizeof(value));

Exploitation & Lab Setup

Red Team

No public exploit code is available. To test this vulnerability in a lab environment:

1. Setup: Deploy SmartDNS from commit 54b4dc on a Linux system (preferably ARM or x86 with alignment checking enabled).
2. Trigger: Send crafted DNS packets or configuration that forces execution of the vulnerable code path in util.c.
3. Observation: Monitor for crashes (SIGBUS) or abnormal behavior. Use tools like valgrind or AddressSanitizer to detect misaligned accesses.

Blue Team

• Detection: Monitor for crashes in SmartDNS processes. Enable alignment checking on x86 (echo 2 > /proc/cpu/alignment) to force SIGBUS on misaligned access.
• Mitigation: If possible, apply a memory-safe wrapper around the vulnerable function. Use compiler flags like -Wcast-align to warn about potential misalignment.
• Workaround: Restrict network access to the SmartDNS service to trusted hosts only.

Indicators of Compromise (IOCs)

• File: smartdns/src/util.c (commit 54b4dc)
• Logs: Repeated SmartDNS crashes with SIGBUS or segmentation faults.
• Network: Unusual DNS queries that may trigger the vulnerable code path.
• Memory: Misaligned pointer values in core dumps.

Detection Engineering

YARA Rule

rule CVE_2024_24198_SmartDNS_Misaligned_Address {
    meta:
        description = "Detects SmartDNS binary compiled from vulnerable commit 54b4dc"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-24198"
    strings:
        $vuln_func = "util.c" ascii wide nocase
        $vuln_commit = "54b4dc" ascii wide nocase
    condition:
        $vuln_func and $vuln_commit
}

Sigma Rule

title: SmartDNS Misaligned Address Crash
id: 3a4b5c6d-7e8f-9a0b-1c2d-3e4f5a6b7c8d
status: experimental
description: Detects SmartDNS process crashes due to misaligned address (CVE-2024-24198)
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/smartdns'
        CommandLine|contains: 'util.c'
    condition: selection
falsepositives:
    - Unknown
level: medium

Suricata Rule

alert dns any any -> any any (msg:"CVE-2024-24198 SmartDNS Misaligned Address Attempt"; flow:to_server; content:"|00 00 00 00|"; depth:4; offset:0; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate: If possible, avoid using SmartDNS commit 54b4dc. Roll back to a previous stable version.
• Long-term: Monitor the SmartDNS repository for an official patch. Apply it as soon as it becomes available.
• Compensating Controls: Run SmartDNS in a sandboxed environment with limited privileges. Use memory protection mechanisms like ASLR and NX.
• Monitoring: Enable detailed logging and alert on SmartDNS crashes.

Valters IT signature