Inefficient Algorithmic Complexity in Linux kernel - CVE-2026-98538

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Main Vulnerability Database Vulnerabilities #VU156840

Inefficient Algorithmic Complexity in Linux kernel - CVE-2026-98538

Published: October 22, 2026


Vulnerability identifier: #VU156840
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-98538
CWE-ID: CWE-407
Exploitation vector: Local access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a local user to cause a denial of service through excessive CPU consumption and soft lockups.

The vulnerability exists due to inefficient algorithmic complexity in cleanup_offline_cgwb() in fs/fs-writeback.c when draining inode lists associated with a dying cgroup writeback instance. A local user can trigger cleanup involving a large number of attached inodes to cause repeated rescanning under wb->list_lock, resulting in quadratic processing time and CPU soft lockups.


Affected software

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

How to mitigate CVE-2026-98538

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

External References

Related Security Bulletins