CVE-2026-89752

Received Received - Intake

Memory Reclaim Race Condition in Linux Kernel

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: mm: memcg: stop reclaim when a limit update is superseded kernfs serializes file operations only per open file, so separate open files can update the same memory.high or memory.max file concurrently. Both handlers store the new limit before synchronous reclaim, but continue to use the writer's local target in the reclaim loop. If another writer raises or removes the limit, the first writer can continue reclaiming toward a stale target. For memory.max, this can leave the writer looping indefinitely once reclaim retries are exhausted. The OOM path sees sufficient margin under the current limit and returns true without killing, while the writer still compares usage against its stale target and records another OOM event. Check the current limit at the start of each reclaim iteration and stop if it no longer matches the writer's target. Reproducer: Populate a cgroup with anonymous memory and disable swapping. Lower memory.max from one open file, then restore it to "max" through another open file after the new limit becomes visible. Without the patch, the first writer remains blocked and repeatedly increments the OOM event counter. With the patch, it returns normally. This was not motivated by a reported production workload. We found it through automated randomized testing for our cgroup observability work and reduced it to the reproducer above.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89752

EUVD

EUVD-2026-76664

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 a race condition in memory cgroup limit updates. When multiple processes update the same memory.high or memory.max file concurrently, the kernel may continue reclaiming memory toward a stale target if another process raises or removes the limit. This can cause indefinite reclaim loops or incorrect OOM handling.

Detection Guidance

This vulnerability is specific to the Linux kernel's memory cgroup (memcg) implementation and requires kernel-level inspection. There are no direct network detection commands. To check for the issue, verify your kernel version against patched releases and inspect cgroup memory.high/memory.max behavior during concurrent writes. Look for indefinite reclaim loops or OOM event counter increments in system logs.

Impact Analysis

This could lead to system instability, excessive CPU usage from continuous reclaim attempts, or incorrect OOM killer behavior. Systems relying on strict memory limits may experience unexpected slowdowns or crashes if the vulnerability is triggered.

Mitigation Strategies

Update your Linux kernel to a version containing the fix for this issue. Monitor cgroup memory limits for unexpected behavior, especially when multiple processes modify memory.high or memory.max concurrently. Disable swapping for affected cgroups as a temporary workaround if updates are delayed.

Hi! I’m here to help you understand CVE-2026-89752. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70