CVE-2026-89752
Description
A flaw was found in the Linux kernel's memory cgroup (memcg) component. When multiple file operations concurrently update memory.high or memory.max files in kernfs, a writer can continue reclaiming memory towards an outdated target. This can lead to an indefinite loop, causing a denial of service (DoS) by blocking the writer and repeatedly incrementing the Out-Of-Memory (OOM) event counter without terminating processes.
Statement
A LOW impact flaw was found in the Linux kernel memory cgroup (memcg) subsystem shipped in Red Hat Enterprise Linux and Red Hat OpenShift Container Platform (RHCOS). Because kernfs serializes file operations only per open file, separate open files can concurrently update the same cgroup memory.high or memory.max limit. A writer that has lowered a limit continues synchronous memory reclaim toward its stale target even after another writer raises or removes that limit; once reclaim retries are exhausted for memory.max, the writer can loop indefinitely, remaining blocked and repeatedly incrementing the OOM event counter without any process being killed. Exploitation requires local access with privileges to modify cgroup memory limits (such as root or CAP_SYS_ADMIN) and a specific concurrent write sequence, so the practical consequence is limited to a local denial of service; the issue was found through automated randomized testing rather than a reported production workload. Red Hat Enterprise Linux 7 (kernel and kernel-rt) is not affected because the vulnerable code is not present. Fixes for the affected Red Hat Enterprise Linux and OpenShift (RHCOS) streams are deferred because the flaw is rated LOW impact, and the residual risk is confined to an already-privileged local user blocking a process that writes cgroup memory limits. The Red Hat CVSS:3.1 score of 5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, moderate) reflects the high availability impact, but Red Hat rates the overall impact LOW given the local privileged access requirement and the narrow trigger conditions.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Alter Execution Logic; Unexpected State
The attacker can gain access to otherwise unauthorized resources.
Integrity,Other
Technical Impact: Modify Application Data; Modify Files or Directories; Modify Memory; Other
Race conditions such as this kind may be employed to gain read or write access to resources which are not normally readable or writable by the user in question.
Integrity,Other
Technical Impact: Other
The resource in question, or other resources (through the corrupted one), may be changed in undesirable ways by a malicious user.
Non-Repudiation
Technical Impact: Hide Activities
If a file or other resource is written in this method, as opposed to in a valid way, logging of the activity may not occur.
Non-Repudiation,Other
Technical Impact: Other
In some cases it may be possible to delete files a malicious user might not otherwise have access to, such as log files.
Other
Technical Impact: Unexpected State
The product may perform invalid actions when the resource is in an unexpected state.
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