CVE-2025-49010: OpenSC Buffer Overflow Vulnerability

CVE-2025-49010 Overview

CVE-2025-49010 is a stack buffer overflow vulnerability affecting OpenSC, an open source smart card tools and middleware package. Prior to version 0.27.0, an attacker with physical access to a computer during token use by a user or administrator can cause a stack-buffer-overflow write in the GET RESPONSE handler. The attack requires a crafted USB device or smart card that presents the system with specially crafted responses to Application Protocol Data Units (APDUs).

Critical Impact

Physical attackers can achieve high confidentiality, integrity, and availability impact through stack-based buffer overflow exploitation during smart card operations.

Affected Products

• OpenSC versions prior to 0.27.0
• Systems using OpenSC middleware for smart card authentication
• Enterprise environments with USB smart card readers

Discovery Timeline

• 2026-03-30 - CVE-2025-49010 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2025-49010

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), which occurs when a program writes data beyond the boundaries of a stack-allocated buffer. In the context of OpenSC, the vulnerability exists in the handling of GET RESPONSE APDUs, which are used to retrieve data from smart cards during cryptographic operations.

The attack requires physical access to the target system and a maliciously crafted USB device or smart card. When a user or administrator interacts with the malicious hardware, specially crafted APDU responses can trigger a stack buffer overflow, potentially allowing arbitrary code execution with the privileges of the user operating the smart card middleware.

Root Cause

The root cause of this vulnerability lies in improper bounds checking when processing APDU responses from smart cards. The GET RESPONSE command, which retrieves pending data from a smart card after an initial command, does not properly validate the length of incoming data before copying it to a stack-allocated buffer. A malicious device can send a response larger than the expected buffer size, causing memory corruption on the stack.

Attack Vector

The attack vector requires physical proximity to the target system. An attacker must either:

1. Connect a malicious USB smart card reader device to the target system
2. Insert a specially crafted smart card into a legitimate reader
3. Compromise an existing smart card reader to inject malicious responses

Once the malicious hardware is connected and a user initiates a smart card operation (such as authentication or signing), the crafted APDU responses trigger the buffer overflow. Due to the physical access requirement, this vulnerability is most concerning in scenarios where attackers can physically access endpoints, such as in supply chain attacks, insider threat scenarios, or targeted attacks against high-value individuals.

The exploitation mechanism involves the smart card middleware receiving an oversized response to a GET RESPONSE APDU command. When the middleware attempts to copy this response into a fixed-size stack buffer without proper length validation, the excess data overwrites adjacent stack memory, including potentially the return address and saved registers.

Detection Methods for CVE-2025-49010

Indicators of Compromise

• Unexpected smart card or USB device connection events on sensitive systems
• Application crashes in OpenSC-related processes (opensc-tool, pkcs11-tool, or applications using OpenSC libraries)
• Stack corruption indicators in system crash dumps from smart card operations
• Unusual APDU response sizes in smart card communication logs

Detection Strategies

• Monitor for abnormal USB device connections, particularly smart card readers from unknown manufacturers
• Implement application crash monitoring for processes that utilize OpenSC middleware
• Deploy endpoint detection rules to identify stack-based exploitation attempts in smart card-related binaries
• Review system logs for repeated authentication failures or crashes during smart card operations

Monitoring Recommendations

• Enable detailed logging for smart card subsystem events
• Configure USB device allowlists to restrict unauthorized smart card readers
• Implement crash dump analysis for applications using PKCS#11 interfaces
• Monitor for unexpected memory access violations in authentication processes

How to Mitigate CVE-2025-49010

Immediate Actions Required

• Upgrade OpenSC to version 0.27.0 or later immediately
• Audit physical access controls for systems using smart card authentication
• Implement USB device whitelisting to prevent unauthorized smart card readers
• Review enterprise smart card deployment for potentially compromised devices

Patch Information

OpenSC has addressed this vulnerability in version 0.27.0. Organizations should update their OpenSC installations to this version or later. The fix implements proper bounds checking for APDU response handling in the GET RESPONSE command processing.

For detailed information about the security fix, refer to the GitHub Security Advisory and the OpenSC CVE Wiki Entry.

Workarounds

• Implement strict USB device policies allowing only known and approved smart card readers
• Disable smart card functionality on systems where it is not required
• Use physical security controls to prevent unauthorized device connections
• Deploy endpoint protection solutions capable of detecting USB-based attacks

# Configuration example: Restrict USB smart card readers using udev rules (Linux)
# Create /etc/udev/rules.d/99-smartcard-restrict.rules
# Only allow specific approved smart card reader vendor/product IDs
SUBSYSTEM=="usb", ATTR{idVendor}=="APPROVED_VENDOR", ATTR{idProduct}=="APPROVED_PRODUCT", MODE="0660", GROUP="scard"
SUBSYSTEM=="usb", ATTR{bInterfaceClass}=="0b", MODE="0000"