CVE-2024-45619

Executive Summary

CVE-2024-45619 is a vulnerability in OpenSC, a set of open-source tools and libraries for working with smart cards and USB cryptographic tokens. The flaw resides in how OpenSC handles APDU (Application Protocol Data Unit) responses from a connected device. An attacker with physical access or the ability to supply a malicious USB device or smart card can craft a response that causes partially filled buffers to be incorrectly accessed. This can lead to an out-of-bounds read or write, potentially resulting in information disclosure, memory corruption, or denial of service. The vulnerability affects OpenSC tools, the PKCS#11 module, the minidriver, and the CTK (Card Tool Kit). No public exploit or proof-of-concept is currently available, and the vendor has not released a patch.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or unassigned value. Based on the description, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Physical (AV:P) – Requires a malicious USB device or smart card.
• Attack Complexity (AC): Low (AC:L) – The crafted response is straightforward.
• Privileges Required (PR): None (PR:N) – No privileges needed to insert the device.
• User Interaction (UI): Required (UI:R) – User must insert the device or card.
• Scope (S): Unchanged (S:U) – The vulnerability affects the host system.
• Confidentiality (C): High (C:H) – Potential memory read.
• Integrity (I): High (I:H) – Potential memory write.
• Availability (A): High (A:H) – Potential crash.

Estimated CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Estimated Base Score: 6.6 (Medium)

Threat Level: Medium. The attack requires physical access or a malicious device, but the impact can be severe.

Deep Dive & Mechanics

The vulnerability is in the APDU response handling within OpenSC. When a smart card or USB token sends a response to an APDU command, OpenSC allocates a buffer to store the response data. If the response is crafted to be shorter than expected or contains specific length fields, the buffer may be only partially filled. The flaw occurs when subsequent code accesses the buffer assuming it is fully initialized, leading to an out-of-bounds read or write.

Root Cause: Improper validation of response length fields in APDU processing. The code does not check that the actual data received matches the expected length before accessing the buffer.

Attack Vector: An attacker creates a malicious USB device (e.g., a modified YubiKey or custom smart card) that responds to APDU commands with a crafted payload. When the user inserts the device and the system uses OpenSC to communicate, the malicious response triggers the vulnerability.

Impact:

• Memory Corruption: Overwriting adjacent memory could lead to code execution.
• Information Disclosure: Reading uninitialized memory could leak sensitive data.
• Denial of Service: A crash could occur.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable pattern.

Vulnerable Code (Conceptual):

// Vulnerable: assumes response length matches expected
unsigned char buffer[256];
int len = apdu_response_length(response);
memcpy(buffer, response_data, len); // len may be larger than actual data
// Later access to buffer assumes it is fully initialized
process_data(buffer, expected_length);

Patched Code (Hypothetical):

// Patched: validate response length
unsigned char buffer[256];
int len = apdu_response_length(response);
if (len > sizeof(buffer) || len < 0) {
    // Error handling
    return -1;
}
memset(buffer, 0, sizeof(buffer)); // Initialize buffer
memcpy(buffer, response_data, len);
// Now safe to access
process_data(buffer, len);

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Hardware: A programmable smart card (e.g., Java Card) or a USB device that can emulate a smart card (e.g., Facedancer).
2. Software: OpenSC tools installed on a test VM (e.g., Ubuntu 22.04 with opensc package).
3. Crafting the Payload: Use a tool like pyApdu or custom C code to send a malicious APDU response.

Exploitation Steps:

1. Insert the malicious device into the target system.
2. The system automatically uses OpenSC to communicate (e.g., via pkcs11-tool or opensc-tool).
3. The device responds with a crafted APDU that has a mismatched length field.
4. The vulnerability triggers, potentially allowing memory corruption.

Note: No public exploit exists; this is a theoretical approach.

Blue Team

Detection:

• Monitor for unusual smart card or USB device activity.
• Use endpoint detection and response (EDR) to detect crashes or memory corruption in OpenSC processes.
• Implement application whitelisting to block unauthorized smart card tools.

Mitigation:

• Disable automatic smart card services if not needed.
• Use only trusted smart cards and USB tokens.
• Apply vendor patches when available.

Indicators of Compromise (IOCs)

• File Hashes: N/A (no known malicious files)
• Process Names: opensc-tool, pkcs11-tool, opensc-daemon
• Network Signatures: N/A (local attack)
• Device Descriptors: USB devices with unusual smart card class descriptors or vendor IDs not in the trusted list.
• Log Entries: System logs showing opensc errors or crashes, e.g., opensc: buffer overflow detected.

Detection Engineering

YARA Rule

rule CVE_2024_45619_OpenSC_APDU_Buffer {
    meta:
        description = "Detects potential exploitation of CVE-2024-45619 via crafted APDU responses"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-45619"
    strings:
        $apdu_response = { 90 00 } // Typical APDU success response
        $buffer_access = { 8B ?? ?? 03 ?? } // Example: mov reg, [reg+offset]
    condition:
        $apdu_response and $buffer_access
}

Sigma Rule

title: CVE-2024-45619 OpenSC APDU Buffer Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2024-45619 via OpenSC process crashes or memory errors
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/opensc-tool'
        CommandLine|contains: '--apdu'
    condition: selection
falsepositives:
    - Legitimate smart card operations
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-45619 OpenSC APDU Buffer Overflow Attempt"; flow:to_server; content:"|90 00|"; depth:2; content:"|FF FF|"; within:10; reference:cve,2024-45619; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable OpenSC services if not required: sudo systemctl disable pcscd
2. Restrict physical access to USB ports and smart card readers.
3. Monitor for suspicious device insertion using USB device control policies.

Long-term Fix:

• Apply vendor patch when released.
• Update OpenSC to a patched version (check https://github.com/OpenSC/OpenSC for updates).
• Implement input validation in custom smart card applications.

Workarounds:

• Use alternative smart card middleware (e.g., libccid with different drivers).
• Enable ASLR and DEP on the host system.

Valters IT