# CVE-2026-89750: tracing/user_events: Clear copied tracing state before fork duplication

> A use-after-free in the Linux kernel tracing subsystem allows local attackers to potentially execute code or escalate privileges via fork duplication errors.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100259, BELL-CVE-2026-89750, DEBIAN-CVE-2026-89750, GHSA-pf29-fjpw-v4g4, UBUNTU-CVE-2026-89750

## What is CVE-2026-89750?

CVE-2026-89750 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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/user_events: Clear copied tracing state before fork duplication

dup_task_struct() copies user_event_mm from the parent into the child,
without grabbing a reference to it. user_event_mm_dup() should
replace it, but it leaves that copied pointer unmodified if
user_event_mm_alloc() fails.

When the child exits, user_event_mm_remove() decrements a reference
the child never owned, which ultimately frees user_event_mm, while
the parent still as a stale pointer to it. This creates a UAF, which
KASAN reports as:

    BUG: KASAN: slab-use-after-free in
    current_user_event_mm+0x51/0x1d0 Write of size 4 at addr
    ffff888005010d30 by task init/44

    Call Trace:
     <TASK>
     kasan_report+0xce/0x100
     kasan_check_range+0x10f/0x1e0
     current_user_event_mm+0x51/0x1d0
     user_events_ioctl+0x82e/0x15c0
     __x64_sys_ioctl+0x139/0x1c0
     do_syscall_64+0xce/0x450
     entry_SYSCALL_64_after_hwframe+0x77/0x7f

    Allocated by task 44:
     __kasan_kmalloc+0x8f/0xa0
     __kmalloc_cache_noprof+0x180/0x3a0
     user_event_mm_alloc+0x3c/0x1f0
     current_user_event_mm+0x88/0x1d0

    Freed by task 42:
     __kasan_slab_free+0x43/0x70
     kfree+0x13a/0x390
     process_one_work+0x696/0xf90
     worker_thread+0x420/0xba0

The fix simply clears the copied pointer before any possible failure.
In case of failure, the child then has nothing to free.

## Which versions are affected by CVE-2026-89750?


## How do I fix CVE-2026-89750?

Apply the vendor's patch.

## Is CVE-2026-89750 being exploited?

There is no known exploitation of CVE-2026-89750 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89750 and fix it if it is affected.

What it is: CVE-2026-89750 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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-2026-89750 in the wild and no public exploit code.

Affected product: Linux. 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-2026-89750/ (Markdown: https://insights.sbomify.com/CVE-2026-89750/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89750
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89750
- OSV: https://osv.dev/vulnerability/CVE-2026-89750

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89750/
Summaries are generated and may contain mistakes; the official description above is the record.