CVE-2017-15031 in Trusted Firmware
Summary
by MITRE
In all versions of ARM Trusted Firmware up to and including v1.4, not initializing or saving/restoring the PMCR_EL0 register can leak secure world timing information.
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Analysis
by VulDB Data Team • 03/25/2026
The vulnerability described in CVE-2017-15031 represents a critical side-channel information leakage issue within ARM Trusted Firmware implementations. This flaw affects all versions up to and including v1.4, making it a widespread concern across numerous embedded systems and secure processing environments. The vulnerability specifically targets the handling of performance monitoring counter registers, particularly PMCR_EL0, which serves as a crucial component in the ARM architecture's performance monitoring capabilities. The issue arises from improper initialization and management of these registers during transitions between secure and non-secure execution worlds, creating potential pathways for timing information leakage that could compromise system security.
The technical root cause of this vulnerability stems from the failure to properly initialize or save/restore the PMCR_EL0 register when transitioning between execution contexts. This register controls performance monitoring functionality and contains critical timing information that can be exploited through side-channel attacks. When the register is not properly managed during context switches, attackers can potentially infer sensitive information about the secure world operations by analyzing timing variations in the system's performance monitoring behavior. The vulnerability is particularly concerning because it operates at the firmware level, where such timing information could reveal details about cryptographic operations, memory access patterns, or other security-sensitive activities that occur within the secure world.
The operational impact of this vulnerability extends beyond simple information leakage, as it fundamentally undermines the security guarantees provided by ARM Trusted Firmware implementations. Attackers could potentially use this timing information to reconstruct cryptographic keys, determine system configurations, or identify security-relevant operational patterns within the secure execution environment. This type of side-channel attack represents a sophisticated threat that aligns with attack techniques documented in the MITRE ATT&CK framework under the 'Credential Access' and 'Defense Evasion' categories. The vulnerability particularly affects systems that rely on ARM TrustZone technology for security isolation, where the secure world must maintain complete confidentiality and integrity of its operations.
The implications of this vulnerability are significant for organizations deploying ARM-based systems with Trusted Firmware, as it creates a persistent threat vector that could remain undetected for extended periods. Systems utilizing ARM processors with TrustZone technology, including mobile devices, embedded systems, and IoT devices, may be vulnerable to timing-based attacks that exploit this register management flaw. The vulnerability's presence in firmware versions up to v1.4 indicates that it has been present for several years, potentially allowing attackers to develop sophisticated exploitation techniques over time. This issue demonstrates the importance of proper register management in secure firmware implementations and highlights the need for comprehensive testing of context switching operations in security-sensitive environments.
Security mitigations for this vulnerability require immediate firmware updates to properly initialize and manage the PMCR_EL0 register during secure world transitions. Organizations should implement comprehensive testing procedures to verify that register state is correctly preserved and restored across execution context switches. The fix typically involves ensuring that the PMCR_EL0 register is properly initialized before secure world operations begin and that its state is correctly saved and restored during context switches. This remediation approach addresses the core issue identified in CWE-248, which relates to improper initialization of resources, and aligns with best practices for secure firmware development. Additionally, system administrators should conduct thorough vulnerability assessments to identify systems running affected firmware versions and prioritize updates to prevent potential exploitation of this timing leakage vulnerability.