CVE-2018-14779 in Yubico-Piv
Summary
by MITRE
A buffer overflow issue was discovered in the Yubico-Piv 1.5.0 smartcard driver. The file lib/ykpiv.c contains the following code in the function `ykpiv_transfer_data()`: {% highlight c %} if(*out_len + recv_len - 2 > max_out) { fprintf(stderr, "Output buffer to small, wanted to write %lu, max was %lu.", *out_len + recv_len - 2, max_out); } if(out_data) { memcpy(out_data, data, recv_len - 2); out_data += recv_len - 2; *out_len += recv_len - 2; } {% endhighlight %} -- it is clearly checked whether the buffer is big enough to hold the data copied using `memcpy()`, but no error handling happens to avoid the `memcpy()` in such cases. This code path can be triggered with malicious data coming from a smartcard.
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Analysis
by VulDB Data Team • 05/02/2023
The vulnerability described in CVE-2018-14779 represents a critical buffer overflow flaw within the Yubico-Piv 1.5.0 smartcard driver ecosystem. This issue exists in the lib/ykpiv.c file within the ykpiv_transfer_data() function, where the software fails to properly validate buffer boundaries before executing memory copy operations. The flaw manifests when processing data received from smartcard devices, creating a scenario where maliciously crafted input can trigger unauthorized memory access patterns.
The technical implementation of this vulnerability demonstrates poor defensive programming practices that directly contravenes established security principles. While the code includes a check to determine if the output buffer can accommodate the incoming data, it lacks proper error handling mechanisms to prevent the memcpy operation from executing when buffer constraints are violated. The conditional logic correctly identifies potential overflow conditions by comparing *out_len + recv_len - 2 against max_out, yet fails to abort execution or return appropriate error codes when this threshold is exceeded. This oversight allows the memcpy() function to proceed with potentially dangerous memory operations, effectively bypassing the protective validation layer.
The operational impact of this buffer overflow vulnerability extends beyond simple memory corruption, as it creates opportunities for arbitrary code execution and system compromise. Attackers can exploit this weakness by crafting malicious smartcard responses that trigger the vulnerable code path, potentially leading to privilege escalation or complete system control. The vulnerability specifically affects the Yubico-Piv smartcard driver, which is commonly used in enterprise security environments for authentication and cryptographic operations, making it particularly dangerous in production systems. According to CWE classification, this represents a classic buffer overflow vulnerability (CWE-121) that falls under the broader category of memory safety issues, while the ATT&CK framework would categorize this as a memory corruption technique (T1067) that could enable privilege escalation (T1068) or code injection (T1059).
Mitigation strategies for this vulnerability should focus on immediate code-level fixes that implement proper error handling and input validation. The primary remediation involves modifying the ykpiv_transfer_data() function to return error codes when buffer overflow conditions are detected, preventing the memcpy() operation from executing in unsafe scenarios. Additionally, developers should implement comprehensive bounds checking throughout the smartcard communication stack, ensuring that all data transfers include proper validation before memory operations occur. Security patches should also include enhanced logging capabilities to detect and alert on suspicious smartcard communications, while system administrators should consider implementing network segmentation and access controls to limit exposure to potentially compromised smartcard devices. The vulnerability underscores the importance of robust input validation and defensive programming practices, particularly in security-critical components such as cryptographic smartcard drivers that handle sensitive authentication data and encryption keys.