---
id: "CVE-2026-99247"
kind: "vulnerability"
aliases: ["CVE-2026-99247"]
title: "Linux kernel: tracing init can dereference a NULL pointer at boot"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["embedded", "infrastructure", "linux-kernel", "servers"]
not_affected_if: ["fixed-kernel", "trace-allocation-succeeds"]
published_at: "2026-11-03T12:17:31+00:00"
first_seen_at: "2026-11-03T12:20:38+00:00"
updated_at: "2026-11-03T12:23:00+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99247", "first_seen_at": "2026-11-03T12:20:38+00:00"}]
---

# Linux kernel: tracing init can dereference a NULL pointer at boot

When trace buffer allocation fails during early boot, the kernel still queues tracefs setup, which reads an uninitialized events list and crashes with a NULL pointer dereference. The fix makes the tracefs setup return early when tracing is disabled.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` to see the running kernel version
- Check whether the kernel includes the fix by looking for the commit 'tracing: Do not initialize tracefs work if tracing is disabled' in your kernel source or distribution changelog

## Timeline

- 2026-11-03T12:20:38+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99247

## From the sources

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

tracing: Do not initialize tracefs work if tracing is disabled

If trace buffer allocation fails during early boot (e.g.  in
early_trace_init() -> allocate_trace_buffers()), tracing_disabled is
left set to 1 and the global trace array events list remains
uninitialized.

Later during boot, tracer_init_tracefs() (invoked via fs_initcall)
queues tracerfs_init_work asynchronously without checking if tracing was
disabled.  When tracer_init_tracefs_work_func() runs, it calls
event_trace_init() and init_tracer_tracefs(&global_trace, NULL)
unconditionally.  This leads to __find_event_file() dereferencing an
uninitialized tr->events list, causing an early boot NULL pointer
dereference Oops:

  BUG: Kernel NULL pointer dereference on read at 0x00000010
  Faulting instruction address: 0xc000000000485be0
  Oops: Kernel access of bad area, sig: 7 [#1]
  ...
  NIP [c000000000485be0] __find_event_file+0x70/0x3c0
  LR  [c000000000448874] init_tracer_tracefs+0x274/0xc80
  Call Trace:
   init_tracer_tracefs+0x274/0xc80
   tracer_init_tracefs_work_func+0x50/0x320
   process_one_work+0x1e8/0x5c0
   worker_thread+0x1dc/0x3d0
   kthread+0x194/0x1b0
   start_kernel_thread+0x14/0x18

Check tracing_disabled at the beginning of tracer_init_tracefs_work_func()
and return immediately if tracing is disabled or failed to initialize,
preventing the crash.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_