CVE-2023-53766 in Linux
Summary
by MITRE • 12/08/2025
In the Linux kernel, the following vulnerability has been resolved:
FS: JFS: Check for read-only mounted filesystem in txBegin
This patch adds a check for read-only mounted filesystem in txBegin before starting a transaction potentially saving from NULL pointer deref.
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Analysis
by VulDB Data Team • 02/23/2026
The vulnerability identified as CVE-2023-53766 resides within the Linux kernel's JFS (Journaled File System) implementation, specifically addressing a critical race condition that could lead to system instability. This flaw manifests during transaction processing when the filesystem is mounted in read-only mode, creating a scenario where improper state validation can result in null pointer dereferences. The issue affects systems utilizing JFS as their primary filesystem, particularly those where read-only mounts are common such as embedded systems, read-only root filesystems, or specialized storage configurations.
The technical root cause of this vulnerability stems from insufficient validation within the transaction beginning function txBegin. When a JFS filesystem is mounted read-only, the system should prevent any write operations from being initiated, yet the original implementation failed to properly check the mount status before attempting transaction commencement. This oversight creates a condition where the transaction subsystem attempts to access memory structures that may not be properly initialized or available in read-only contexts, leading to potential null pointer dereferences that could crash the kernel or expose system stability. The vulnerability represents a classic case of inadequate input validation and state management within kernel space operations.
The operational impact of CVE-2023-53766 extends beyond simple system crashes, potentially enabling denial of service conditions that could affect critical infrastructure systems relying on JFS. Attackers could exploit this vulnerability by mounting a JFS filesystem in read-only mode and then triggering transaction processing, which could lead to kernel panics or system reboots. This type of vulnerability is particularly concerning in embedded systems, storage appliances, or any environment where JFS is used as a filesystem and where system availability is paramount. The vulnerability aligns with CWE-476 which addresses NULL pointer dereference issues, and could potentially map to ATT&CK technique T1499.004 related to network disruption through system resource exhaustion or kernel-level instability.
The patch addressing this vulnerability implements a straightforward yet critical validation check within the txBegin function to ensure that transactions are not initiated on read-only mounted filesystems. This mitigation approach prevents the problematic code path from executing when the filesystem is in read-only mode, thereby eliminating the potential for null pointer dereference conditions. The fix demonstrates proper defensive programming practices by validating preconditions before executing potentially dangerous operations, aligning with secure coding principles that emphasize early validation and proper state management. Systems administrators should prioritize applying this patch across all Linux systems utilizing JFS filesystems, particularly those with read-only mount configurations, to prevent potential exploitation scenarios that could lead to system instability or denial of service conditions.