External risk intelligence

Linux Kernel OCFS2 DLM Off-by-One Error

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-53309

This vulnerability is located within the OCFS2 (Oracle Cluster File System version 2) distributed lock manager code in the Linux kernel. This component operates at the kernel level for internal cluster management and data synchronization, and is not exposed to the public internet in standard deployment patterns.

Linux Kernel

2.6.37 to before 5.10.2585.11 to before 5.15.2095.16 to before 6.1.1756.2 to before 6.6.1416.7 to before 6.12.916.13 to before 6.18.336.19 to before 7.0.10

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A recently resolved issue in the Linux kernel could potentially allow unauthorized access and modification of data. The vulnerability involves an off-by-one error in how regions are compared within the cluster file system's distributed lock manager. While the main concern is confirming relevance and exposure, understanding this type of kernel-level issue is important for overall system integrity.

Kernel logic error affects data access.
Matters for system integrity and trust.
Confirm relevance; kernel issue, not direct threat.

Attack Path

How an attacker could exploit the issue

An attacker could reach this vulnerability by interacting with the Linux kernel's distributed lock manager, specifically within the OCFS2 file system. This interaction could involve sending specially crafted data that is processed by the `dlm_match_regions()` function, leading to an out-of-bounds read. If successful, this could allow an attacker to compromise the confidentiality, integrity, and availability of the system.

Requires access to the Linux kernel.
Triggered by flawed region comparison logic.
Risk of data compromise and system disruption.

Live Threat

Current exploitation, exposure, and threat context

A flaw in the Linux kernel's OCFS2 distributed lock manager could allow an attacker to read data beyond its intended boundaries. This condition could affect system data integrity and potentially lead to unauthorized information disclosure, particularly in clustered file system environments.

System data integrity.
Reading beyond valid memory ranges.
Disclosure of sensitive system information.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability resides in the Linux kernel's OCFS2 component, specifically within the distributed lock manager. Infrastructure or platform teams managing Linux systems and OCFS2 deployments are likely responsible for remediation. The initial step involves identifying all systems running the affected kernel component, assessing their exposure and criticality, and then planning a coordinated update during a maintenance window.

Infrastructure or platform teams own this.
Verify OCFS2 deployment and reachability.
Plan kernel updates during maintenance.

Supplementary metadata

CVSS vector

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Frequently asked questions

What is the Linux kernel OCFS2 component?

OCFS2, or Oracle Cluster File System version 2, is a shared-disk file system for Linux. It is designed for high-performance clusters, allowing multiple servers to access the same storage simultaneously. It manages data consistency across these nodes using a Distributed Lock Manager (DLM) to coordinate file access and prevent conflicts.

What does CVE-2026-53309 mean by an off-by-one error?

This is a memory safety issue where the software calculates a boundary incorrectly. In this case, the DLM logic compares memory regions using an improper mathematical operator. Because it checks one too many entries, it reads past the intended memory buffer, which is a common class of flaw that can lead to system instability or unauthorized data access.

How is this OCFS2 vulnerability triggered?

The flaw is triggered when the kernel executes the dlm_match_regions function to compare cluster regions. It does not occur during routine file system operations that stay within defined limits. Exploitation would require an attacker to influence the input processed by this specific internal lock management routine, rather than simply interacting with standard file system commands.

Is my system at risk from this OCFS2 issue?

Halo Surface Signal indicates that this vulnerability exists within internal cluster management code, making it very unlikely to be reachable from the public internet in standard setups. You should focus on systems specifically configured with OCFS2. If your infrastructure does not utilize this cluster file system, this vulnerability is not relevant to your environment.

What should I do if I run OCFS2?

First, inventory your systems to identify where OCFS2 is active. Since this is a kernel-level issue, remediation involves applying the provided kernel patches. Coordinate with your platform teams to schedule these updates during a regular maintenance window to ensure system stability while addressing the underlying logic flaw.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.