# CVE-2026-23088: tracing: Fix crash on synthetic stacktrace field usage

> A local attacker with root privileges can crash the Linux kernel by configuring specific synthetic tracing events that dereference a null pointer.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Feb 2026
- **Updated:** 23 May 2026
- **Also known as:** AZL-77145, BELL-CVE-2026-23088, DEBIAN-CVE-2026-23088, GHSA-3gp7-mv7f-66rh, ROOT-OS-DEBIAN-11-CVE-2026-23088, ROOT-OS-DEBIAN-12-CVE-2026-23088, ROOT-OS-UBUNTU-2204-CVE-2026-23088, ROOT-OS-UBUNTU-2404-CVE-2026-23088, UBUNTU-CVE-2026-23088

## What is CVE-2026-23088?

CVE-2026-23088 is a medium-severity vulnerability in Linux kernel, published on 4 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

tracing: Fix crash on synthetic stacktrace field usage

When creating a synthetic event based on an existing synthetic event that
had a stacktrace field and the new synthetic event used that field a
kernel crash occurred:

 ~# cd /sys/kernel/tracing
 ~# echo 's:stack unsigned long stack[];' > dynamic_events
 ~# echo 'hist:keys=prev_pid:s0=common_stacktrace if prev_state & 3' >> events/sched/sched_switch/trigger
 ~# echo 'hist:keys=next_pid:s1=$s0:onmatch(sched.sched_switch).trace(stack,$s1)' >> events/sched/sched_switch/trigger

The above creates a synthetic event that takes a stacktrace when a task
schedules out in a non-running state and passes that stacktrace to the
sched_switch event when that task schedules back in. It triggers the
"stack" synthetic event that has a stacktrace as its field (called "stack").

 ~# echo 's:syscall_stack s64 id; unsigned long stack[];' >> dynamic_events
 ~# echo 'hist:keys=common_pid:s2=stack' >> events/synthetic/stack/trigger
 ~# echo 'hist:keys=common_pid:s3=$s2,i0=id:onmatch(synthetic.stack).trace(syscall_stack,$i0,$s3)' >> events/raw_syscalls/sys_exit/trigger

The above makes another synthetic event called "syscall_stack" that
attaches the first synthetic event (stack) to the sys_exit trace event and
records the stacktrace from the stack event with the id of the system call
that is exiting.

When enabling this event (or using it in a historgram):

 ~# echo 1 > events/synthetic/syscall_stack/enable

Produces a kernel crash!

 BUG: unable to handle page fault for address: 0000000000400010
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: Oops: 0000 [#1] SMP PTI
 CPU: 6 UID: 0 PID: 1257 Comm: bash Not tainted 6.16.3+deb14-amd64 #1 PREEMPT(lazy)  Debian 6.16.3-1
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
 RIP: 0010:trace_event_raw_event_synth+0x90/0x380
 Code: c5 00 00 00 00 85 d2 0f 84 e1 00 00 00 31 db eb 34 0f 1f 00 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 2e 0f 1f 84 00 00 00 00 00 <49> 8b 04 24 48 83 c3 01 8d 0c c5 08 00 00 00 01 cd 41 3b 5d 40 0f
 RSP: 0018:ffffd2670388f958 EFLAGS: 00010202
 RAX: ffff8ba1065cc100 RBX: 0000000000000000 RCX: 0000000000000000
 RDX: 0000000000000001 RSI: fffff266ffda7b90 RDI: ffffd2670388f9b0
 RBP: 0000000000000010 R08: ffff8ba104e76000 R09: ffffd2670388fa50
 R10: ffff8ba102dd42e0 R11: ffffffff9a908970 R12: 0000000000400010
 R13: ffff8ba10a246400 R14: ffff8ba10a710220 R15: fffff266ffda7b90
 FS:  00007fa3bc63f740(0000) GS:ffff8ba2e0f48000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000400010 CR3: 0000000107f9e003 CR4: 0000000000172ef0
 Call Trace:
  <TASK>
  ? __tracing_map_insert+0x208/0x3a0
  action_trace+0x67/0x70
  event_hist_trigger+0x633/0x6d0
  event_triggers_call+0x82/0x130
  trace_event_buffer_commit+0x19d/0x250
  trace_event_raw_event_sys_exit+0x62/0xb0
  syscall_exit_work+0x9d/0x140
  do_syscall_64+0x20a/0x2f0
  ? trace_event_raw_event_sched_switch+0x12b/0x170
  ? save_fpregs_to_fpstate+0x3e/0x90
  ? _raw_spin_unlock+0xe/0x30
  ? finish_task_switch.isra.0+0x97/0x2c0
  ? __rseq_handle_notify_resume+0xad/0x4c0
  ? __schedule+0x4b8/0xd00
  ? restore_fpregs_from_fpstate+0x3c/0x90
  ? switch_fpu_return+0x5b/0xe0
  ? do_syscall_64+0x1ef/0x2f0
  ? do_fault+0x2e9/0x540
  ? __handle_mm_fault+0x7d1/0xf70
  ? count_memcg_events+0x167/0x1d0
  ? handle_mm_fault+0x1d7/0x2e0
  ? do_user_addr_fault+0x2c3/0x7f0
  entry_SYSCALL_64_after_hwframe+0x76/0x7e

The reason is that the stacktrace field is not labeled as such, and is
treated as a normal field and not as a dynamic event that it is.

In trace_event_raw_event_synth() the event is field is still treated as a
dynamic array, but the retrieval of the data is considered a normal field,
and the reference is just the meta data:

// Meta data is retrieved instead of a dynamic array
---truncated---

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23088?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23088?

Apply the vendor's patch.

## Is CVE-2026-23088 being exploited?

There is no known exploitation of CVE-2026-23088 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23088 and fix it if it is affected.

What it is: CVE-2026-23088 is a medium-severity vulnerability in Linux kernel, published on 4 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23088 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-23088/ (Markdown: https://insights.sbomify.com/CVE-2026-23088/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23088
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23088
- OSV: https://osv.dev/vulnerability/CVE-2026-23088

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23088/
Summaries are generated and may contain mistakes; the official description above is the record.