CVE-2021-43613 in InsydeH2O
Summary
by MITRE • 09/03/2026
An issue was discovered in SysPasswordDxe in Insyde InsydeH2O. User and administrator password hashes are exposed in runtime UEFI variables, leading to escalation of privilege
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Analysis
by VulDB Data Team • 09/03/2026
The vulnerability identified within the SysPasswordDxe component of the Insyde H2O Unified Extensible Firmware Interface (UEFI) firmware represents a critical failure in secure credential management at the pre-boot stage. This flaw specifically affects how user and administrator password hashes are stored and accessed during system runtime, exposing sensitive authentication data that should remain isolated within protected memory regions or hardware-backed security modules. In modern computing architectures, UEFI variables serve as non-volatile storage for configuration settings passed between the firmware and operating systems. However, in this specific implementation, these variables containing hashed passwords were not adequately restricted by access control policies defined in the Security Descriptor Definition Language (SDDL). Consequently, any entity with sufficient privileges to read standard runtime UEFI variables can retrieve these hashes without requiring elevated system rights or physical interaction beyond booting a malicious operating system image.
From a technical perspective, this issue stems from an improper implementation of Access Control Lists for specific firmware variables associated with password storage. Typically, sensitive data such as BIOS passwords should be stored in non-observable variables that are inaccessible to the Operating System after handoff, or they must be encrypted using keys derived from hardware-specific secrets like TPM-bound keys. The exposure described indicates a misconfiguration where the visibility attribute of these variables allows read access by OS-level processes. This creates a direct pathway for attackers who have gained initial foothold on the system through other means to extract password hashes. Once obtained, these hashes can be subjected to offline brute-force or dictionary attacks without triggering lockout mechanisms typically enforced at login prompts, thereby bypassing standard account protection policies.
The operational impact of this vulnerability is severe, primarily facilitating privilege escalation from a low-privileged user context to that of an administrator or root equivalent. An attacker leveraging this flaw does not need to exploit complex memory corruption bugs; instead, they rely on the inherent design weakness in how firmware handles credential storage. By extracting the password hashes, the adversary can crack them offline using high-performance computing resources. Upon successful cracking, the attacker gains full administrative control over the operating system and potentially deeper access into the UEFI environment itself. This level of access allows for persistent malware installation, modification of boot sequences to load malicious kernels before security software initializes, or complete data exfiltration with elevated privileges that are difficult to detect using standard endpoint detection tools designed to monitor runtime application behavior rather than firmware-level interactions.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) identifiers such as CWE-284 Improper Access Control and CWE-359 Exposure of Private Information, specifically regarding the exposure of sensitive data through improper variable permissions. Furthermore, in the context of the MITRE ATT&CK framework for firmware attacks, this flaw supports techniques related to persistence via UEFI bootkit installation or credential dumping from non-volatile storage. The ability to read these hashes effectively neutralizes one of the primary layers of defense provided by BIOS/UEFI passwords, rendering them ineffective against determined adversaries with local access.
Mitigation strategies must focus on correcting the security descriptors associated with the affected UEFI variables in future firmware updates released by Insyde Software Corp. Administrators should ensure that their systems are updated to versions where these variables are either marked as non-observable or encrypted using hardware-bound keys inaccessible to standard OS processes. In environments where immediate patching is not feasible, organizations should enforce strict physical security controls and utilize full-disk encryption solutions like BitLocker with TPM integration, which can help mitigate the risk of data exposure even if password hashes are compromised. Additionally, disabling unnecessary UEFI variable access through group policies or secure boot configurations may reduce the attack surface until a definitive firmware patch is deployed across all affected devices.