CVE-2018-16420 in OpenSC
Summary
by MITRE
Several buffer overflows when handling responses from an ePass 2003 Card in decrypt_response in libopensc/card-epass2003.c in OpenSC before 0.19.0-rc1 could be used by attackers able to supply crafted smartcards to cause a denial of service (application crash) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 05/06/2023
The vulnerability identified as CVE-2018-16420 represents a critical buffer overflow condition within the OpenSC library's handling of smartcard responses, specifically affecting the ePass 2003 Card implementation. This flaw exists in the decrypt_response function located within the libopensc/card-epass2003.c source file and affects all versions of OpenSC prior to 0.19.0-rc1. The vulnerability stems from inadequate input validation and bounds checking when processing responses from the ePass 2003 smartcard, creating a potential attack surface where maliciously crafted card responses could trigger memory corruption issues. The flaw falls under the CWE-121 CWE category, which encompasses buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory boundaries, potentially leading to application instability or arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as the buffer overflow could potentially enable more sophisticated attacks depending on the execution environment and memory layout. When an application using OpenSC processes responses from a compromised ePass 2003 card, the insufficient validation allows attackers to craft specific response payloads that exceed the allocated buffer space, causing memory corruption that manifests as application crashes or unpredictable behavior. This vulnerability is particularly concerning in security-sensitive environments where smartcard authentication systems are deployed, as it could be exploited to disrupt critical authentication processes or potentially provide a foothold for more advanced attacks. The attack vector requires physical access to the smartcard or the ability to supply crafted card responses, making it a privilege escalation or supply chain attack vector rather than a network-based vulnerability.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1059.007, which covers command and control communications, as the buffer overflow could potentially be leveraged to manipulate application behavior or gain unauthorized access to authentication systems. The vulnerability's impact classification as both denial of service and unspecified other impacts suggests that while immediate system disruption is the primary concern, there exists potential for more severe consequences including privilege escalation or information disclosure. Organizations utilizing OpenSC for smartcard-based authentication should consider this vulnerability in their risk assessment frameworks, particularly in environments where smartcard readers are accessible to untrusted parties or where the system components are deployed in security-critical applications. The mitigation strategy involves upgrading to OpenSC version 0.19.0-rc1 or later, which includes proper bounds checking and input validation mechanisms that prevent the buffer overflow conditions from occurring during response processing.
The technical nature of this vulnerability demonstrates the importance of robust input validation in cryptographic libraries and smartcard handling components. The flaw represents a classic example of how insufficient security controls in middleware components can create cascading effects throughout security infrastructures. Security practitioners should recognize that vulnerabilities of this nature often require careful consideration of the entire attack surface, particularly in environments where multiple authentication mechanisms interact with smartcard infrastructure. The fix implemented in OpenSC 0.19.0-rc1 addresses the root cause by implementing proper buffer size validation and ensuring that response data is properly bounded before processing, thereby preventing the overflow conditions that could lead to system instability or potential exploitation. This vulnerability underscores the critical need for comprehensive security testing of cryptographic libraries and smartcard implementations, particularly in enterprise environments where authentication systems form the foundation of security infrastructure.