CVE-2020-11684 in AT91bootstrap
Summary
by MITRE
AT91bootstrap before 3.9.2 does not properly wipe encryption and authentication keys from memory before passing control to a less privileged software component. This can be exploited to disclose these keys and subsequently encrypt and sign the next boot stage (such as the bootloader).
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Analysis
by VulDB Data Team • 09/14/2020
The vulnerability identified as CVE-2020-11684 affects AT91bootstrap versions prior to 3.9.2 and represents a critical security flaw in embedded system firmware development. This issue stems from inadequate memory management practices during the boot process, specifically concerning how cryptographic keys are handled when transitioning control to subsequent software components. The vulnerability resides in the improper disposal of encryption and authentication keys from memory regions that are subsequently accessed by less privileged software components, creating a persistent security risk throughout the boot chain.
The technical implementation flaw manifests when AT91bootstrap fails to perform thorough memory wiping operations before transferring control to downstream boot stages. This oversight creates a scenario where sensitive cryptographic material remains accessible in memory even after initial boot processes have completed. The vulnerability is classified under CWE-254 as a "Weakness in Memory Management" and specifically relates to improper handling of sensitive data during system transitions. Attackers can exploit this weakness to extract encryption keys and authentication credentials that should have been securely cleared from memory, potentially enabling them to compromise the entire boot process.
The operational impact of this vulnerability extends far beyond simple information disclosure, as it fundamentally undermines the security model of the embedded system. When attackers can extract cryptographic keys from memory, they gain the capability to encrypt and sign subsequent boot stages, effectively allowing them to replace or modify critical system components without detection. This creates a persistent backdoor that can survive system reboots and potentially compromise the integrity of the entire boot chain. The vulnerability directly maps to ATT&CK technique T1542.001 for "Taint Runtime Execution" and T1542.002 for "Preload Libraries" as attackers can manipulate the boot process through compromised cryptographic material.
The security implications are particularly severe for embedded systems that rely on secure boot mechanisms, as this vulnerability essentially nullifies the cryptographic protections designed to prevent unauthorized modifications to the boot process. The compromised keys can be used to sign malicious code that will be accepted by the system's verification mechanisms, creating a persistent threat that can evade traditional security controls. Organizations implementing AT91bootstrap in critical infrastructure, automotive systems, or industrial control environments face significant risk from this vulnerability, as it can lead to complete system compromise and unauthorized access to sensitive operational data. The recommended mitigation involves upgrading to AT91bootstrap version 3.9.2 or later, which implements proper memory wiping procedures before control transfer, and conducting thorough security assessments of all boot stages to ensure cryptographic material is properly secured throughout the system lifecycle.