CVE-2026-23271 Linux CVE debrief

Who should care

Linux kernel maintainers, distro security teams, and operators of multi-user Linux systems should care most. This is especially relevant where local users, containers, or shared hosts can interact with perf events or related BPF-enabled code paths.

Technical summary

The CVE description says __perf_event_overflow() was not guaranteed to run with IRQs disabled across all callchains. In some software-event paths it could execute with only preemption disabled, creating a race against perf_event_exit_event() and related teardown that frees resources the overflow path still expects to access. The result is a use-after-free style timing bug in kernel perf event handling. The supplied record maps this to CVSS 3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, indicating local exploitation conditions and high potential impact if triggered.

Defensive priority

High. This is a kernel-level race in a widely used subsystem, with local attack requirements but high impact potential. Systems that expose perf-related functionality to less-trusted users should be prioritized for patching.

Recommended defensive actions

• Apply the Linux kernel fix versions or vendor backports that address __perf_event_overflow() vs perf_remove_from_context() race handling.
• Prioritize patching on multi-user systems, shared development hosts, and environments where local users may access perf events.
• Review any hardening or access-control policies around perf_event and related kernel performance monitoring features.
• Track distro advisories and kernel stable updates associated with the linked upstream fixes.
• If immediate patching is not possible, reduce exposure to untrusted local users on affected systems until updates are deployed.

Evidence notes

All claims here are limited to the supplied CVE description, the NVD record, and the linked Linux kernel stable references. The NVD record shows CVE-2026-23271 published on 2026-03-20 and modified on 2026-04-02, with vulnStatus listed as 'Undergoing Analysis' in the provided source item. The description explicitly names the race between __perf_event_overflow() and perf_remove_from_context()/perf_event_exit_event(), and notes the BPF program as state that may be freed before the overflow path finishes. No exploit procedure or unverified impact claims are included.

Official resources