CVE-2018-6875 in KeepKey
Summary
by MITRE
Format String vulnerability in KeepKey version 4.0.0 allows attackers to trigger information display (of information that should not be accessible), related to text containing characters that the device's font lacks.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 01/13/2020
The CVE-2018-6875 vulnerability represents a format string flaw in KeepKey hardware wallet version 4.0.0 that exposes critical security risks through improper text handling mechanisms. This vulnerability specifically manifests when the device encounters text strings containing characters that fall outside its supported font set, creating an exploitable condition where attackers can manipulate the device's display behavior to reveal sensitive information. The flaw stems from inadequate input validation and sanitization processes within the device's text rendering subsystem, which fails to properly handle malformed or unsupported character sequences during display operations.
The technical exploitation of this vulnerability occurs through carefully crafted input that triggers the format string behavior in the device's firmware. When the KeepKey processes text containing unsupported font characters, the device's text rendering engine attempts to display these characters using default formatting mechanisms that inadvertently expose memory contents or internal device state information. This represents a classic format string vulnerability pattern where attacker-controlled input influences the formatting of output, potentially revealing stack contents, memory addresses, or other sensitive data that should remain confidential. The vulnerability is particularly concerning because it operates at the display layer, where sensitive information such as private keys, wallet balances, or cryptographic material might be inadvertently exposed through malformed text rendering.
From an operational impact perspective, this vulnerability compromises the fundamental security assurances that hardware wallets provide to users. The exposure of sensitive information through display manipulation can lead to unauthorized access to cryptocurrency wallets, potentially resulting in financial loss for users. The vulnerability affects the device's ability to maintain proper information hiding principles, which are essential for hardware security modules. Security researchers have identified this issue as a potential vector for information disclosure attacks that could be leveraged in combination with other vulnerabilities to escalate privileges or extract cryptographic keys from the device's secure elements. The flaw impacts the device's integrity and confidentiality properties, undermining the trust model that hardware wallets are designed to maintain.
Mitigation strategies for CVE-2018-6875 should focus on implementing robust input validation and sanitization mechanisms within the device's text processing pipeline. Firmware updates must include proper handling of unsupported character sets through graceful degradation or character substitution mechanisms rather than allowing format string behaviors to occur. Security measures should incorporate comprehensive testing of text rendering functions with various character inputs, including Unicode characters and special formatting sequences, to prevent similar vulnerabilities from manifesting. The vulnerability aligns with CWE-134 which specifically addresses format string vulnerabilities where format strings are constructed from user-controlled data, and it maps to ATT&CK technique T1059.001 for command and scripting interpreter usage in exploitation contexts. Organizations should implement regular security assessments of firmware components and maintain updated threat intelligence to address similar vulnerabilities in hardware security devices, particularly focusing on input validation controls and secure text rendering practices that prevent information leakage through display mechanisms.