CVE-2020-8432 in Das U-Boot
Summary
by MITRE
In Das U-Boot through 2020.01, a double free has been found in the cmd/gpt.c do_rename_gpt_parts() function. Double freeing may result in a write-what-where condition, allowing an attacker to execute arbitrary code. NOTE: this vulnerablity was introduced when attempting to fix a memory leak identified by static analysis.
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Analysis
by VulDB Data Team • 03/27/2024
The vulnerability identified as CVE-2020-8432 represents a critical memory corruption issue within Das U-Boot bootloader version 2020.01 and earlier. This flaw exists in the command line interface implementation specifically within the gpt.c source file, where the do_rename_gpt_parts() function contains a problematic memory management pattern. The vulnerability was inadvertently introduced during an attempt to address a previously identified memory leak through static analysis tools, demonstrating how security fixes can sometimes introduce new attack vectors.
The technical nature of this vulnerability stems from a double free condition occurring in the GPT partition table renaming functionality. When the do_rename_gpt_parts() function executes, it performs memory deallocation operations that are subsequently called twice on the same memory block. This memory management error creates a scenario where freed memory can be reallocated and manipulated by an attacker. The double free condition directly maps to CWE-415, which describes improper double free conditions in software implementations. The resulting write-what-where condition allows an attacker to control both the memory address and the data being written, providing a pathway for arbitrary code execution within the bootloader context.
The operational impact of this vulnerability extends beyond simple code execution, as it affects the fundamental integrity of the system boot process. An attacker who can manipulate the GPT partition table through the command interface gains the ability to execute malicious code during the early boot phase, potentially compromising the entire system security posture. This vulnerability is particularly concerning because it exists within a bootloader component that operates with high privileges and directly influences system initialization. The attack surface becomes significant when considering that many embedded systems and network devices rely on U-Boot for their boot process, making this a widespread concern across various device types.
Mitigation strategies for CVE-2020-8432 require immediate patch application to update Das U-Boot to versions 2020.04 or later where the double free issue has been resolved. Organizations should also implement runtime protections such as memory protection mechanisms and heap sanitization tools to detect and prevent exploitation attempts. The fix typically involves correcting the memory deallocation logic to ensure each allocated memory block is freed exactly once, preventing the conditions that lead to the write-what-where scenario. Security teams should also monitor for related vulnerabilities in similar memory management patterns within the U-Boot codebase, as this incident demonstrates the potential for seemingly benign fixes to introduce new security weaknesses. From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as exploitation would likely involve manipulating command line parameters to trigger the vulnerable code path, and T1068 for exploit for privilege escalation, since successful exploitation would enable execution with bootloader privileges.