# CVE-2025-39829: trace/fgraph: Fix the warning caused by missing unregister notifier

> A missing unregister notifier in the Linux kernel fgraph tracer can trigger a warning and potential instability when function profiling is toggled.

- **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:** 16 Sep 2025
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-71209, BELL-CVE-2025-39829, DEBIAN-CVE-2025-39829, GHSA-qgx7-pghq-36xv, ROOT-OS-DEBIAN-11-CVE-2025-39829, ROOT-OS-DEBIAN-12-CVE-2025-39829, ROOT-OS-UBUNTU-2204-CVE-2025-39829, ROOT-OS-UBUNTU-2404-CVE-2025-39829, UBUNTU-CVE-2025-39829

## What is CVE-2025-39829?

CVE-2025-39829 is a medium-severity denial of service vulnerability in Linux kernel, published on 16 Sep 2025. 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:

trace/fgraph: Fix the warning caused by missing unregister notifier

This warning was triggered during testing on v6.16:

notifier callback ftrace_suspend_notifier_call already registered
WARNING: CPU: 2 PID: 86 at kernel/notifier.c:23 notifier_chain_register+0x44/0xb0
...
Call Trace:
 <TASK>
 blocking_notifier_chain_register+0x34/0x60
 register_ftrace_graph+0x330/0x410
 ftrace_profile_write+0x1e9/0x340
 vfs_write+0xf8/0x420
 ? filp_flush+0x8a/0xa0
 ? filp_close+0x1f/0x30
 ? do_dup2+0xaf/0x160
 ksys_write+0x65/0xe0
 do_syscall_64+0xa4/0x260
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

When writing to the function_profile_enabled interface, the notifier was
not unregistered after start_graph_tracing failed, causing a warning the
next time function_profile_enabled was written.

Fixed by adding unregister_pm_notifier in the exception path.

## Which versions are affected by CVE-2025-39829?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39829?

Apply the vendor's patch.

## Is CVE-2025-39829 being exploited?

There is no known exploitation of CVE-2025-39829 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-2025-39829 and fix it if it is affected.

What it is: CVE-2025-39829 is a medium-severity denial of service vulnerability in Linux kernel, published on 16 Sep 2025. 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-2025-39829 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-2025-39829/ (Markdown: https://insights.sbomify.com/CVE-2025-39829/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39829
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39829
- OSV: https://osv.dev/vulnerability/CVE-2025-39829

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39829/
Summaries are generated and may contain mistakes; the official description above is the record.