CVE-2020-10125 in SelfServ ATM
Summary
by MITRE
NCR SelfServ ATMs running APTRA XFS 04.02.01 and 05.01.00 implement 512-bit RSA certificates to validate bunch note acceptor (BNA) software updates, which can be broken by an attacker with physical access in a sufficiently short period of time, thereby enabling the attacker to sign arbitrary files and CAB archives used to update BNA software, as well as bypass application whitelisting, resulting in the ability to execute arbitrary code.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 11/04/2025
The vulnerability described in CVE-2020-10125 affects NCR SelfServ ATMs that utilize APTRA XFS version 04.02.01 and 05.01.00 for managing note acceptance functionality. These ATM systems implement 512-bit RSA certificates for authenticating software updates to the bunch note acceptor component, which represents a significant cryptographic weakness in the security architecture. The use of such short RSA key lengths creates a critical exposure that directly violates industry standards and best practices for cryptographic security. According to CWE-326, this vulnerability represents an implementation weakness where insufficient cryptographic strength is employed, making the system susceptible to cryptanalytic attacks that would otherwise be computationally infeasible with properly sized keys.
The technical flaw lies in the implementation of 512-bit RSA encryption for software update authentication, which has been demonstrated to be vulnerable to modern computational attacks. This cryptographic weakness allows an attacker with physical access to the ATM to perform a brute force or factorization attack against the RSA certificate within a reasonable timeframe. The vulnerability specifically targets the bunch note acceptor software update mechanism, which is a critical component responsible for processing cash deposits. The attacker can leverage this weakness to generate valid signatures for arbitrary files and CAB archives, effectively bypassing the intended security controls that are designed to prevent unauthorized modifications to the BNA software.
The operational impact of this vulnerability extends beyond simple code execution capabilities to encompass complete system compromise through bypass of application whitelisting mechanisms. When an attacker successfully breaks the 512-bit RSA certificate, they gain the ability to sign malicious software updates that will be accepted by the ATM system, allowing for arbitrary code execution within the context of the BNA software. This represents a critical escalation from simple privilege escalation to full system compromise, as the attacker can effectively take control of the cash handling functionality while maintaining operational stealth. The vulnerability's impact aligns with ATT&CK technique T1059.007 for command and scripting interpreter and T1068 for exploit for privilege escalation, as it provides a pathway for persistent access and system manipulation.
The security implications of this vulnerability are particularly severe given the physical access requirement and the nature of ATM environments where such access might be obtained through social engineering or by exploiting physical security weaknesses. The 512-bit RSA key size was considered inadequate even when the system was initially deployed, as it falls well below the minimum recommended key lengths for modern cryptographic implementations. Organizations implementing these systems should consider this vulnerability as a high-risk exposure that requires immediate remediation through either firmware updates, cryptographic key rotation, or complete system replacement. The vulnerability demonstrates the critical importance of maintaining up-to-date cryptographic standards and proper key management practices as outlined in NIST SP 800-57 and ISO/IEC 14443 standards for secure authentication mechanisms in financial systems.