# CVE-2026-31481

> Vulnerability · severity: **MEDIUM** (CVSS 5.5).

## Description

In the Linux kernel, the following vulnerability has been resolved:

tracing: Drain deferred trigger frees if kthread creation fails

Boot-time trigger registration can fail before the trigger-data cleanup
kthread exists. Deferring those frees until late init is fine, but the
post-boot fallback must still drain the deferred list if kthread
creation never succeeds.

Otherwise, boot-deferred nodes can accumulate on
trigger_data_free_list, later frees fall back to synchronously freeing
only the current object, and the older queued entries are leaked
forever.

To trigger this, add the following to the kernel command line:

  trace_event=sched_switch trace_trigger=sched_switch.traceon,sched_switch.traceon

The second traceon trigger will fail and be freed. This triggers a NULL
pointer dereference and crashes the kernel.

Keep the deferred boot-time behavior, but when kthread creation fails,
drain the whole queued list synchronously. Do the same in the late-init
drain path so queued entries are not stranded there either.

## Key facts

- **CVE ID:** CVE-2026-31481
- **Published:** 2026-04-22
- **CVSS severity:** MEDIUM
- **CVSS base score:** 5.5
- **CWE codes:** CWE-476

## Affected products

- `linux:linux_kernel`

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31481

## Citation

> AI Analytics. CVE-2026-31481. Retrieved 2026-07-23 from https://api.ai-analytics.org/cve/CVE-2026-31481. Derived from NIST NVD. Licensed CC0.

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