CVE-2018-16422 in OpenSC
Summary
by MITRE
A single byte buffer overflow when handling responses from an esteid Card in sc_pkcs15emu_esteid_init in libopensc/pkcs15-esteid.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-2018-16422 represents a critical buffer overflow flaw within the OpenSC project's implementation of PKCS#15 emulation for Estonian smartcards. This issue exists in the sc_pkcs15emu_esteid_init function located in the libopensc/pkcs15-esteid.c source file, affecting all versions prior to the 0.19.0-rc1 release. The flaw manifests as a single byte buffer overflow when processing responses from esteid Cards, which are widely used for digital authentication and signature purposes in Estonia's e-government infrastructure. The vulnerability specifically targets the parsing logic that handles communication between the OpenSC library and Estonian smartcards, creating a potential attack surface for malicious actors who can manipulate the card's response data.
The technical implementation of this vulnerability stems from inadequate bounds checking within the response handling code, where the application fails to properly validate the length of data received from the smartcard before attempting to copy it into a predetermined buffer space. This classic buffer overflow scenario occurs when the received data exceeds the allocated buffer size by a single byte, causing memory corruption that can lead to application instability. The flaw operates at the interface level between the cryptographic library and hardware token, making it particularly dangerous as it can be triggered through legitimate card communication channels. According to CWE classification, this represents a CWE-121: Stack-based Buffer Overflow, while the ATT&CK framework would categorize this under T1059.007: Command and Scripting Interpreter: PowerShell and T1203: Exploitation for Client Execution, as attackers could leverage this to execute arbitrary code or cause denial of service.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, potentially enabling more sophisticated attacks depending on the execution environment and system configuration. When exploited, the buffer overflow can cause the OpenSC application to crash abruptly, disrupting legitimate authentication processes and potentially creating denial of service conditions for systems relying on smartcard-based authentication. The unspecified other impacts mentioned in the vulnerability description suggest that under certain conditions, attackers might be able to achieve arbitrary code execution or information disclosure, particularly in environments where OpenSC is used for critical security functions. This vulnerability is particularly concerning for organizations utilizing Estonian smartcards for digital signatures, authentication, and secure communications, as it could compromise the integrity of the entire authentication infrastructure. The attack vector requires an adversary to either physically interact with a smartcard or manipulate the card's response data through a man-in-the-middle attack, making it a significant concern for systems where such physical access or network-level manipulation is possible.
Mitigation strategies for CVE-2018-16422 primarily focus on immediate software updates to versions 0.19.0-rc1 or later, where the buffer overflow has been resolved through proper bounds checking and input validation. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing OpenSC are updated promptly, particularly those handling sensitive authentication data. Additional defensive measures include network segmentation to limit physical access to smartcard readers, implementation of secure communication protocols between applications and card readers, and regular monitoring for unusual application behavior that might indicate exploitation attempts. Security teams should also consider implementing intrusion detection systems capable of identifying anomalous communication patterns that could indicate attempts to exploit this vulnerability. The vulnerability highlights the importance of proper input validation in cryptographic libraries and demonstrates the critical need for thorough security testing of hardware-software interfaces, particularly those handling sensitive authentication data in government and enterprise environments. Organizations should also conduct regular security assessments of their smartcard infrastructure to identify and remediate similar vulnerabilities that might exist in other components of their authentication systems.