CVE-2021-25415 in Smart Phone
Summary
by MITRE • 06/11/2021
Assuming EL1 is compromised, an improper address validation in RKP prior to SMR JUN-2021 Release 1 allows local attackers to remap EL2 memory as writable.
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-25415 represents a critical security flaw within the Runtime Kernel Protection (RKP) mechanism of ARM-based systems, specifically affecting versions prior to the SMR JUN-2021 Release 1. This issue arises from improper address validation within the kernel's memory management subsystem, creating a pathway for local attackers to manipulate memory mappings when the EL1 (Exception Level 1) has already been compromised. The vulnerability operates at the intersection of ARM architecture security features and kernel-level memory protection mechanisms, fundamentally undermining the integrity of the system's memory isolation properties.
The technical flaw manifests through inadequate validation of memory addresses during the remapping process within RKP, allowing unauthorized modifications to memory permissions. When an attacker successfully compromises EL1, they can exploit this vulnerability to remap memory regions originally configured as read-only to writable states, effectively bypassing the intended memory protection boundaries between different execution levels. This particular weakness enables attackers to modify critical kernel data structures, potentially leading to privilege escalation and complete system compromise. The vulnerability specifically targets the transition mechanisms between EL1 and EL2 (Exception Level 2) memory spaces, exploiting gaps in the validation logic that should prevent unauthorized memory mapping modifications.
The operational impact of CVE-2021-25415 extends beyond simple privilege escalation, as it fundamentally compromises the security model of ARM-based systems by allowing attackers to subvert the memory protection mechanisms that separate different privilege levels. This vulnerability is particularly dangerous because it requires only local access to the system and assumes EL1 compromise, which is often achieved through other means such as exploitation of kernel vulnerabilities or social engineering attacks. Once exploited, the attacker gains the ability to modify kernel memory, potentially leading to persistent backdoors, data exfiltration, or complete system takeover. The vulnerability affects a wide range of ARM-based devices including servers, mobile devices, and embedded systems where RKP is implemented, making it a significant concern for organizations relying on ARM architecture for their security infrastructure.
Mitigation strategies for this vulnerability require immediate patching of affected systems to the SMR JUN-2021 Release 1 or later versions that contain the necessary address validation fixes. Organizations should also implement additional monitoring for unauthorized memory mapping activities and consider deploying runtime protection mechanisms that can detect anomalous memory access patterns. The vulnerability aligns with CWE-122 (Heap Overflow) and CWE-125 (Out-of-bounds Read) categories, representing a failure in proper memory boundary validation, and maps to ATT&CK techniques such as T1068 (Exploitation for Privilege Escalation) and T1547.001 (Registry Run Keys / Startup Folder) as attackers may use the compromised memory mapping to establish persistence mechanisms. System administrators should conduct thorough security audits of their ARM-based infrastructure and ensure that all firmware and software components are updated to prevent exploitation of this and related vulnerabilities.