CVE-2017-7563 in Trusted Firmware
Summary
by MITRE
In ARM Trusted Firmware 1.3, RO memory is always executable at AArch64 Secure EL1, allowing attackers to bypass the MT_EXECUTE_NEVER protection mechanism. This issue occurs because of inconsistency in the number of execute-never bits (one bit versus two bits).
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Analysis
by VulDB Data Team • 06/08/2026
The vulnerability identified as CVE-2017-7563 represents a critical security flaw in ARM Trusted Firmware version 1.3 that fundamentally undermines memory protection mechanisms at the AArch64 Secure EL1 execution level. This issue stems from an inconsistency in the implementation of execute-never bits within the memory management subsystem, creating a pathway for attackers to bypass essential security controls designed to prevent code execution from read-only memory regions. The flaw specifically affects the Trusted Firmware implementation and has significant implications for systems relying on ARM's security architecture for protecting sensitive operations and data.
The technical root cause of this vulnerability lies in the inconsistent handling of execute-never bits within the memory management unit of the ARM architecture. When the firmware operates at Secure EL1 level, it maintains a memory protection mechanism that should prevent execution of code from read-only memory regions through the MT_EXECUTE_NEVER protection. However, the implementation contains a discrepancy where the system expects two execute-never bits for proper memory protection while only utilizing one bit in practice. This inconsistency creates a condition where memory regions designated as read-only can still be executed, effectively nullifying the security boundary that should separate trusted and untrusted code execution spaces.
The operational impact of this vulnerability is severe and multifaceted, particularly for systems implementing ARM TrustZone technology and relying on secure execution environments. Attackers can exploit this weakness to execute malicious code within the secure world, potentially compromising the integrity of sensitive operations and data processing. This vulnerability directly enables privilege escalation attacks and undermines the fundamental security model of ARM-based trusted execution environments. The flaw affects systems where the ARM Trusted Firmware is used to establish secure contexts, including mobile devices, embedded systems, and IoT devices that depend on ARM's security extensions for protecting confidential information and cryptographic operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-119, which addresses memory protection issues and improper access to memory regions. The flaw also relates to ATT&CK technique T1068, which involves local privilege escalation through kernel or firmware vulnerabilities. Organizations implementing ARM-based security solutions must recognize that this vulnerability could enable attackers to gain unauthorized access to secure processing environments, potentially compromising the entire security infrastructure of devices relying on ARM TrustZone technology. The implications extend beyond simple code execution, as attackers could potentially access cryptographic keys, sensitive data, or other protected resources within the secure world.
Mitigation strategies for CVE-2017-7563 require immediate firmware updates from ARM and device manufacturers to address the execute-never bit inconsistency. System administrators should ensure that all affected devices receive the latest firmware patches that correct the memory management implementation. Additionally, organizations should conduct comprehensive security assessments of their ARM-based systems to identify potential exploitation vectors and implement additional monitoring for suspicious execution patterns. The vulnerability highlights the importance of rigorous testing and validation of memory protection mechanisms in security-critical firmware implementations, particularly in environments where multiple security layers must work cohesively to maintain system integrity and confidentiality.