CVE-2026-74414 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
hfsplus: Remove the duplicate attr inode dirty marking action
Syzbot reported a null-ptr-deref in [1].
If the attributes file is not loaded during system mount, a trigger occurs [1] when setxattr is executed in userspace.
Remove the first mark attr inode dirty operation.
[1]
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
Call Trace: hfsplus_setxattr+0x124/0x340 fs/hfsplus/xattr.c:555 hfsplus_trusted_setxattr+0x40/0x60 fs/hfsplus/xattr_trusted.c:30 __vfs_setxattr+0x43c/0x480 fs/xattr.c:218 __vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:252 vfs_setxattr+0x163/0x360 fs/xattr.c:339 do_setxattr fs/xattr.c:654 [inline]
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides within the Linux kernel's hfsplus filesystem implementation where a race condition and improper null pointer handling leads to potential system instability. This issue manifests when the attributes file fails to load during system mount operations, creating a scenario where subsequent userspace setxattr calls trigger a null pointer dereference. The root cause stems from duplicate inode dirty marking actions that occur in the xattr.c file at line 555 within the hfsplus_setxattr function. When the system attempts to mark an attribute inode as dirty without proper validation of whether the attributes file has been successfully loaded, the kernel encounters a null pointer dereference at memory addresses ranging from 0x0000000000000008 to 0x000000000000000f. This vulnerability directly relates to CWE-476 which describes null pointer dereference conditions in software systems.
The operational impact of this vulnerability extends beyond simple system crashes as it represents a potential attack vector for privilege escalation or denial of service scenarios. When an unprivileged user executes setxattr operations on hfsplus mounted filesystems, the kernel's failure to properly validate attribute file loading status creates a path for exploitation. The KASAN (Kernel Address Sanitizer) report confirms the exact memory access violation that occurs during this process, demonstrating how the system attempts to dereference a null pointer when accessing attribute inode data structures. This behavior can be leveraged by malicious actors to destabilize systems running hfsplus filesystems, particularly in environments where such filesystems are mounted with user-accessible attributes.
The fix implemented addresses the core issue by removing the redundant first mark attr inode dirty operation that was causing the null pointer dereference. This modification ensures proper synchronization and validation of attribute file loading states before attempting any inode dirty marking operations. The solution follows established kernel security practices for preventing double-free conditions and improper resource handling, aligning with ATT&CK technique T1068 which involves exploiting local privilege escalation vulnerabilities through kernel flaws. By eliminating the duplicate marking operation, the kernel now properly handles cases where attribute files are not loaded during mount, preventing the null pointer dereference that would otherwise occur during setxattr execution.
The remediation approach demonstrates proper defensive programming practices and follows security guidelines for kernel module development. The fix reduces complexity in the filesystem code path while maintaining functional integrity of the hfsplus implementation. This vulnerability highlights the importance of proper resource initialization and validation before attempting operations on potentially uninitialized data structures, particularly in kernel space where such failures can lead to system-wide instability. The resolution ensures that attribute inode dirty marking only occurs when appropriate, preventing both the immediate null pointer dereference and potential cascading failures that could occur in more complex exploitation scenarios involving multiple concurrent filesystem operations.