CVE-2026-89169 in live-boot
Summary
by MITRE • 09/11/2026
live-boot ff8867c allows attackers to bypass the dm-verity-enforce-roothash-signature protection mechanism when the .verity file is missing.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in live-boot, specifically associated with commit hash ff8867c, represents a critical security flaw within the system initialization process of Linux-based operating systems that utilize dm-verity for root filesystem integrity verification. This issue directly impacts the effectiveness of the dm-verity-enforce-roothash-signature protection mechanism, which is designed to ensure that the booting kernel and root filesystem have not been tampered with by verifying cryptographic signatures against a known good roothash. The core technical flaw lies in the conditional logic governing how live-boot handles cases where the expected .verity file, containing the necessary metadata for integrity verification, is absent from the system or installation media. Instead of failing securely and halting the boot process to prevent potential compromise, the implementation incorrectly proceeds with initialization without enforcing the signature check when this specific configuration artifact is missing.
From a technical perspective, dm-verity operates by creating a device mapper target that verifies blocks of data against a Merkle tree hash stored in metadata. When the system attempts to enforce roothash signatures, it relies on the presence of these verification structures to validate the integrity chain from the bootloader down to the root filesystem. The absence of the .verity file indicates either a misconfiguration or an incomplete installation environment where the integrity data is not available for validation. In such scenarios, the vulnerable code path fails to trigger a secure failure state. This oversight allows the system to continue booting with an unverified root image, effectively nullifying the security guarantees provided by dm-verity in that specific context. An attacker who can influence or manipulate the environment during deployment could exploit this gap to introduce malicious modifications to the operating system binaries without detection.
The operational impact of this vulnerability is significant for environments relying on live-boot scenarios, such as forensic analysis tools, secure boot demonstrations, or temporary administrative sessions where integrity verification is paramount. By bypassing the dm-verity-enforce-roothash-signature mechanism, an adversary could achieve code execution with root privileges if they can replace the underlying filesystem images before boot time. This undermines the trust model of the system, as the fundamental assumption that the booted software matches a known good baseline is violated without alerting the user or administrator. The vulnerability essentially creates a backdoor through configuration omission rather than complex exploitation techniques, making it particularly dangerous in automated deployment pipelines where missing files might be overlooked during routine checks.
This flaw aligns with CWE-258, which describes an empty password or lack of authentication check that allows unauthorized access, and more specifically relates to CWE-693, Protection Mechanism Failure, as the security control intended to protect against tampering is bypassed due to improper implementation logic. In terms of MITRE ATT&CK mapping, this vulnerability facilitates Initial Access and Persistence by allowing an attacker to deploy a compromised system image that appears legitimate but lacks integrity verification. It also supports Defense Evasion techniques where attackers modify system files while evading detection mechanisms designed to catch such changes. The failure to enforce security controls when expected data is missing represents a classic case of insecure default configurations or error handling flaws in critical infrastructure components.
Mitigation strategies must focus on ensuring that the live-boot environment strictly enforces integrity checks regardless of file presence, or alternatively, fails securely if verification data cannot be obtained. Developers should modify the boot scripts to detect the absence of the .verity file and explicitly abort the boot process with a clear error message indicating an integrity check failure rather than proceeding silently. Additionally, system administrators deploying live-boot environments should verify that all necessary cryptographic metadata files are present and correctly formatted before initiating the boot sequence. Implementing strict input validation for configuration states and ensuring that security mechanisms do not degrade gracefully into insecure states is essential to maintaining the integrity of Linux-based systems in sensitive operational contexts.