CVE-2025-13763: libopensc Information Disclosure Flaw

CVE-2025-13763 Overview

Multiple uses of uninitialized variables were discovered in libopensc, the library component of the OpenSC project that provides support for smart cards and USB cryptographic tokens. This vulnerability could lead to information disclosure or application crashes when a system processes specially crafted responses from a malicious USB device or smart card.

Critical Impact

Exploitation requires physical access to the target system via a crafted USB device or smart card. A successful attack can result in disclosure of sensitive memory contents or denial of service through application crashes.

Affected Products

• libopensc (OpenSC library)
• OpenSC smart card middleware
• Systems using OpenSC for USB token or smart card authentication

Discovery Timeline

• 2026-04-23 - CVE-2025-13763 published to NVD
• 2026-04-23 - Last updated in NVD database

Technical Details for CVE-2025-13763

Vulnerability Analysis

This vulnerability is classified as CWE-457 (Use of Uninitialized Variable). When libopensc processes Application Protocol Data Unit (APDU) responses from connected smart cards or USB cryptographic tokens, multiple code paths fail to properly initialize variables before use. This allows an attacker with physical access to present a specially crafted device that returns malformed APDU responses, triggering the use of uninitialized memory.

The uninitialized variable usage can lead to two primary impacts: sensitive information stored in stack or heap memory may be inadvertently disclosed to the attacker, or the application may crash when dereferencing garbage values as pointers or using them in critical operations.

Root Cause

The root cause stems from insufficient variable initialization in libopensc code paths that handle APDU response processing. When the library receives responses from a connected device, certain variables are conditionally initialized based on response content. Maliciously crafted responses can bypass these initialization paths while still allowing execution to continue with uninitialized values, violating the fundamental assumption that these variables contain valid data.

Attack Vector

The attack requires physical proximity and access to the target system. An attacker must connect a specially crafted USB device or smart card that emulates a legitimate cryptographic token but provides malicious APDU responses. When the target system's OpenSC library attempts to communicate with the device, the crafted responses trigger code paths where uninitialized variables are used, leading to memory disclosure or crashes.

The physical access requirement and high attack complexity significantly limit the exploitability of this vulnerability in most scenarios. However, it remains a concern in environments where untrusted USB devices may be connected, such as kiosks, shared workstations, or systems with physical security vulnerabilities.

Detection Methods for CVE-2025-13763

Indicators of Compromise

• Unexpected crashes in applications using libopensc or OpenSC utilities
• Unusual USB device connection events followed by application failures
• Memory corruption or segmentation fault errors in OpenSC-related processes
• Anomalous smart card authentication failures paired with system instability

Detection Strategies

• Monitor system logs for crashes in processes linked against libopensc
• Implement USB device whitelisting to restrict connections to known, trusted cryptographic tokens
• Enable application crash monitoring and analysis for OpenSC-related binaries
• Deploy endpoint detection tools capable of identifying anomalous USB device behavior

Monitoring Recommendations

• Configure centralized logging for smart card and USB token authentication events
• Set up alerts for repeated authentication failures or unusual APDU communication patterns
• Monitor for new or unknown USB device connections in high-security environments
• Implement application crash telemetry for systems using OpenSC middleware

How to Mitigate CVE-2025-13763

Immediate Actions Required

• Review OpenSC project advisories for updated versions addressing this vulnerability
• Restrict physical access to systems using OpenSC for authentication
• Implement USB device whitelisting to prevent connections from untrusted devices
• Monitor for abnormal behavior from systems using smart card authentication

Patch Information

Consult the GitHub Security Advisory GHSA-2v44-fq35-98vv for official patch information and fixed versions. Additional details are available in the OpenSC CVE-2025-13763 Wiki and Red Hat CVE-2025-13763 Advisory.

Workarounds

• Implement strict USB device policies that only allow pre-approved cryptographic tokens
• Use hardware-based USB port blockers in high-security environments
• Deploy endpoint protection solutions that can detect and block malicious USB devices
• Consider network-based authentication alternatives where physical token security cannot be guaranteed

# Example: Restrict USB device access on Linux systems using udev rules
# Add to /etc/udev/rules.d/99-usb-security.rules
# Allow only specific trusted smart card vendor/product IDs
SUBSYSTEM=="usb", ATTR{idVendor}=="TRUSTED_VENDOR_ID", ATTR{idProduct}=="TRUSTED_PRODUCT_ID", MODE="0660", GROUP="smartcard"
# Deny all other USB smart card devices by default
SUBSYSTEM=="usb", ATTR{bInterfaceClass}=="0b", MODE="0000"