CVE-2026-23043 in Linux
Summary
by MITRE • 02/04/2026
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix NULL pointer dereference in do_abort_log_replay()
Coverity reported a NULL pointer dereference issue (CID 1666756) in do_abort_log_replay(). When btrfs_alloc_path() fails in replay_one_buffer(), wc->subvol_path is NULL, but btrfs_abort_log_replay() calls do_abort_log_replay() which unconditionally dereferences wc->subvol_path when attempting to print debug information. Fix this by adding a NULL check before dereferencing wc->subvol_path in do_abort_log_replay().
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability identified as CVE-2026-23043 represents a critical NULL pointer dereference flaw within the Linux kernel's btrfs file system implementation. This issue manifests specifically in the do_abort_log_replay() function where the kernel attempts to access a pointer that may not have been properly initialized, leading to potential system crashes or unauthorized access conditions. The vulnerability was discovered through Coverity static analysis tools which flagged a code path where btrfs_alloc_path() failure results in an uninitialized pointer being dereferenced during error handling operations.
The technical flaw occurs within the btrfs subvolume recovery mechanism where the function replay_one_buffer() encounters a failure during path allocation through btrfs_alloc_path(). When this allocation fails, the wc->subvol_path variable remains NULL, but the subsequent call to btrfs_abort_log_replay() which invokes do_abort_log_replay() proceeds to unconditionally dereference this NULL pointer during debug output generation. This creates a classic null pointer dereference condition that can result in kernel oops messages, system instability, or potentially exploitable crash conditions that could be leveraged by malicious actors to disrupt system operations.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the integrity of btrfs file system operations and overall system stability. When triggered, the NULL pointer dereference can cause the kernel to panic and reboot the entire system, creating denial of service conditions that affect critical infrastructure. The vulnerability is particularly concerning in environments where btrfs is extensively used for storage management, as it could be exploited to cause sustained service disruption or potentially provide a foothold for more sophisticated attacks. This flaw aligns with CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations.
From a security perspective, this vulnerability represents a potential attack vector that could be exploited in privilege escalation scenarios or denial of service attacks against systems running btrfs file systems. The issue demonstrates poor error handling practices within kernel space code where proper null checks are not performed before pointer access, creating opportunities for system instability. The ATT&CK framework would categorize this as a system crash or hang technique that could be used to disrupt normal operations or as part of a broader attack chain leading to privilege escalation. Organizations utilizing btrfs file systems should prioritize patching this vulnerability to prevent potential exploitation and maintain system integrity.
The fix for this vulnerability requires implementing a simple but crucial NULL pointer validation check before accessing wc->subvol_path in the do_abort_log_replay() function. This defensive programming approach ensures that the code gracefully handles the case where btrfs_alloc_path() fails and prevents the kernel from attempting to dereference an uninitialized pointer. The patch demonstrates the importance of robust error handling in kernel space code and reinforces the principle that all pointers should be validated before access, particularly in critical system components where failures can have cascading effects on overall system stability and security posture.