# CVE-2026-89746: tracing: Fix use-after-free with same-name named triggers

> A use-after-free in Linux kernel tracing allows local attackers to cause a kernel panic or potentially execute code via crafted hist triggers.

- **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-100169, BELL-CVE-2026-89746, DEBIAN-CVE-2026-89746, GHSA-m56h-pfxh-qxq7, UBUNTU-CVE-2026-89746

## What is CVE-2026-89746?

CVE-2026-89746 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: Fix use-after-free with same-name named triggers

When two hist triggers on different events are registered with the same
name=, the second one reuses the first as named_data.  Both are added to
tr->hist_vars by save_hist_vars() during event_hist_trigger_parse(),
because save_hist_vars() is called before event_trigger_register() while
the named reuse is only detected later, in hist_register_trigger().

In the named-data branch hist_register_trigger() then frees the second
histogram's hist_data via destroy_hist_data(), but never removes its
tr->hist_vars list entry, leaving a dangling pointer and leaking the
trace_array reference it holds.

A later hist trigger that references a variable makes find_var_file()
walk tr->hist_vars and dereference the freed hist_data.  The bug is
reproducible from userspace by writing three hist triggers to tracefs:

  cd /sys/kernel/tracing
  echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_switch/trigger
  echo 'hist:keys=common_pid:x=common_pid:name=mh' > events/sched/sched_process_fork/trigger
  echo 'hist:keys=common_pid:vals=$x' > events/sched/sched_process_exit/trigger

The third write panics the kernel:

  BUG: KASAN: slab-use-after-free in find_var_file.part.0+0x272/0x290
  Read of size 8 at addr ffff888001f8a0e0 by task sh/1
  CPU: 1 UID: 0 PID: 1 Comm: sh Tainted: G      D          N
  Call Trace:
    find_var_file.part.0
    find_event_var
    parse_atom
    parse_expr
    __create_val_field
    event_hist_trigger_parse
    trigger_process_regex
    event_trigger_write
    vfs_write
    ksys_write
    do_syscall_64
    entry_SYSCALL_64_after_hwframe
  Allocated by task 1:
    event_hist_trigger_parse
  Freed by task 1:
    hist_register_trigger+0x618/0xa30
    event_hist_trigger_parse
  The buggy address belongs to freed 2048-byte region
  Oops: general protection fault ... RIP: find_var_file.part.0
  Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b

Fix by removing the hist_data from tr->hist_vars and releasing the
trace_array reference in the named-data branch of hist_register_trigger()
before freeing the hist_data.

## Which versions are affected by CVE-2026-89746?


## How do I fix CVE-2026-89746?

Apply the vendor's patch.

## Is CVE-2026-89746 being exploited?

There is no known exploitation of CVE-2026-89746 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89746 and fix it if it is affected.

What it is: CVE-2026-89746 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-2026-89746 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-2026-89746/ (Markdown: https://insights.sbomify.com/CVE-2026-89746/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89746
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89746
- OSV: https://osv.dev/vulnerability/CVE-2026-89746

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89746/
Summaries are generated and may contain mistakes; the official description above is the record.