CVE-2026-89502

A flaw was found in the Linux kernel's ring-buffer component. When sub-buffers are configured with a specific memory allocation order greater than zero, the system attempts to free a memory page using an incorrect size. This memory management error can lead to memory corruption, potentially allowing a local attacker to escalate privileges or cause a system crash (Denial of Service).

A low impact flaw was found in the Linux kernel's tracing ring-buffer implementation. When a ring buffer is configured with sub-buffers using a memory allocation order greater than 0, the per-CPU spare page (cpu_buffer->free_page) is freed using an incorrect order, causing incorrect memory deallocation and potential kernel memory corruption. Exploitation requires local access to a system whose tracing ring buffer uses such a configuration. Red Hat's assessment rates the consequences as availability only (CVSS:3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H): the practical impact is a system crash (denial of service). Although the upstream description notes that memory corruption could in principle allow privilege escalation, no such path is established by the current evidence.

Red Hat Enterprise Linux 6, 7, 8, and 9 (kernel and kernel-rt) are not affected because the vulnerable code is not present in those kernels, and OpenShift Container Platform 4 versions (RHEL CoreOS) are not affected for the same reason; the affected code was introduced upstream in kernel version 6.8. The currently affected Red Hat offerings include OpenShift Container Platform 5.0 and 5.1, for which the fix is deferred. The deferral reflects the low impact of this flaw: it requires local access, is confined to the tracing ring-buffer free path, and only manifests when larger sub-buffer orders are configured. The residual risk on such systems is kernel memory corruption leading to a system crash, with no direct confidentiality or integrity impact.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

This issue only manifests when the kernel tracing ring buffer is configured with sub-buffer memory allocation orders greater than 0. Configuring tracing ring buffers to use order-0 sub-buffers avoids triggering the incorrect free. For the affected Red Hat offerings the fix is currently deferred; affected kernels should be updated once a fixed kernel is released for the corresponding update stream. Upstream, this issue is resolved in current stable kernel releases.