Cloudanix VulnDB

CVE-2026-89752

None

CVSS

—

EPSS

0.2%

Published

Sep 11, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A flaw in how the operating system updates memory limits for groups of processes can cause it to keep trying to free memory even after the limit has been removed, leading to repeated false error reports.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Denial Of Service
Component
OS kernel
Class
Race Condition
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Race condition in memcg limit handlers allows concurrent writers to memory.max or memory.high to continue reclaim loops against a stale target value after the limit is raised or removed by another writer, leading to indefinite blocking on memory.max once reclaim retries are exhausted and repeated OOM event counter increments without an actual OOM kill.

Why it matters to the business

Systems running affected kernels may experience unnecessary repeated OOM event logging, blocked processes, and degraded observability for memory cgroup limits, increasing operational noise and potential for missed real issues in containerized or virtualized workloads.

How an attack unfolds

An attacker with the ability to open multiple file descriptors to the same memory.max or memory.high cgroup file can issue concurrent limit updates; the first writer stores its target and enters reclaim, while the second update supersedes the limit, yet the first writer continues using the stale target, resulting in repeated OOM events or indefinite loops.

How to fix it

Update to a Linux kernel containing the fix that checks the current limit value at the start of each reclaim iteration and aborts if it no longer matches the writer's original target; apply the latest stable kernel for the distribution in use.

How to confirm the fix worked

Confirm the presence of the upstream commit that adds the limit check inside the reclaim loop; test the provided reproducer scenario and verify that OOM event counters no longer increment after the limit is raised through a second open file.

Typical attack path

  1. Open multiple file descriptors to the same memory cgroup limit file
  2. Issue a restrictive memory.max update via the first descriptor
  3. Issue a relaxing or removal update via the second descriptor before the first reclaim loop completes
  4. Observe the first writer continuing reclaim against the stale target and incrementing OOM counters

How to detect it

Search kernel logs and cgroup event counters for repeated OOM events on cgroups where memory.max was recently updated through multiple open files; correlate with processes blocked in reclaim.

What your security team should do

  • Prioritize kernel updates on systems with heavy cgroup memory limit usage
  • Monitor cgroup OOM event counters for unexpected spikes
  • Review container runtime and orchestration configurations that rely on memory.max settings

The record

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.

Affected packages

Ecosystem Package Introduced Fixed