CVE-2026-74596 in Linux
Summary
by MITRE • 08/22/2026
In the Linux kernel, the following vulnerability has been resolved:
fs,fsverity: remove check for fsverity being enabled in setattr_prepare()
The check that fs-verity is available in the kernel is not necessary here. Filesystems could have fsverity files even without fs-verity enabled. In that case, truncate on fsverity file will succeed, what this check is trying to prevent.
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Analysis
by VulDB Data Team • 08/22/2026
The Linux kernel vulnerability identified involves an incorrect validation logic within the filesystem verity subsystem, specifically in the setattr_prepare function of the VFS layer. This issue stems from a redundant and logically flawed check that verifies whether fs-verity support is enabled at compile time before allowing attribute changes on files protected by file system verity. The core technical flaw lies in the assumption that if the kernel was not compiled with CONFIG_FS_VERITY, then no files can possess verity metadata or attributes. This assumption fails to account for scenarios where a filesystem image containing fs-verity protected files is mounted on a system running a kernel without native fs-verity support enabled. In such cases, the file may still retain its extended attributes and inode flags indicating verity protection, even though the active kernel cannot enforce them.
The operational impact of this vulnerability centers on the handling of truncate operations for these specific files. When an application attempts to modify file attributes, particularly truncating a file that has fs-verity enabled via metadata but lacks runtime enforcement due to the missing kernel feature, the flawed check incorrectly blocks or mishandles the operation depending on interpretation. However, as described in the resolution context, the primary concern was preventing unintended side effects during attribute changes. The presence of this unnecessary check could lead to unexpected behavior where valid administrative actions are blocked, or conversely, if bypassed improperly, it might allow operations that compromise data integrity assumptions. While fs-verity is primarily designed for read-only integrity verification and typically restricts writes, the interaction with setattr_prepare highlights a deeper issue in how kernel features interact with static file metadata across different system configurations.
From a standards perspective, this vulnerability aligns with CWE-20 Improper Input Validation, as the code fails to correctly validate the relationship between compile-time feature flags and runtime file state. It also touches upon CWE-841 Improvement of Action Inconsistency because the behavior differs based on whether fs-verity is enabled in the kernel versus present in the filesystem metadata. Within the MITRE ATT&CK framework, while this is not a direct exploitation vector for remote code execution or privilege escalation, it relates to Defense Evasion techniques where an attacker might attempt to manipulate file attributes to bypass security controls if they can influence system configuration or exploit misconfigurations. The vulnerability represents a logic error rather than a memory corruption issue, emphasizing the importance of robust state management in kernel subsystems.
The resolution involves removing the superfluous check for fs-verity being enabled in setattr_prepare(). By eliminating this condition, the kernel allows attribute changes to proceed based on the actual file system capabilities and standard permission checks rather than compile-time flags. This ensures that filesystems with verity files function correctly even when the host kernel does not support fs-verity natively. The mitigation strategy for administrators involves ensuring that systems handling such images are properly configured, but more importantly, it highlights the need for developers to decouple runtime feature availability from static metadata validation where appropriate. For system maintainers, applying this patch is critical to maintaining consistent behavior across heterogeneous kernel configurations and preventing potential denial of service through blocked administrative operations on verity-enabled files.