CVE-2026-74401

Received Received - Intake

DLM Message Sequence Ordering Flaw in Linux Kernel

Publication date: 2026-08-15

Last updated on: 2026-08-17

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: dlm: fix add msg handle in send_queue ordered In a benchmark scenario triggering a lot of requests that triggers a lot of DLM messages on the network it can be that the mh->seq is not ordered according the oldest seq number. This ordering is required by dlm_receive_ack as "before(mh->seq, seq)" will stop to check for older sequence numbers that are ordered in the tail of "node->send_queue". The side effects of not having it correct ordered regarding "before(mh->seq, seq)" are refcounting issues and use-after free. I only was able to reproduce this issue in a experimental DLM branch and a user space DLM benchmark that uses io_uring. After changing this I don't experienced any refcounting with the sending buffer issues anymore.

CVSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-17

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-74401

EUVD

EUVD-2026-59548

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves incorrect ordering of DLM (Distributed Lock Manager) messages in the send_queue. When many requests trigger numerous DLM messages, the sequence numbers may not be ordered correctly. This breaks a requirement in dlm_receive_ack where older sequence numbers must be checked first. The result is refcounting issues and potential use-after-free vulnerabilities.

Detection Guidance

This vulnerability is specific to the Linux kernel's DLM (Distributed Lock Manager) subsystem and requires a benchmark scenario triggering many DLM messages. Detection would involve monitoring DLM message ordering and refcounting issues in the kernel logs or through kernel tracing tools like ftrace or perf.

Impact Analysis

The vulnerability can lead to memory corruption issues like use-after-free and incorrect reference counting. This may cause system instability, crashes, or unexpected behavior in applications relying on DLM for distributed locking. It was only reproducible in experimental setups, suggesting limited real-world impact but still poses a risk in specific configurations.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a low-level Linux kernel issue related to DLM message ordering, causing refcounting problems and potential use-after-free errors. No evidence suggests it impacts data protection, privacy, or security controls required by these regulations.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for this vulnerability. Monitor DLM message sequences for ordering issues and refcounting errors in kernel logs.

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