# CVE-2026-97923: tracing: Free histogram the var ref when its initialization fails

> A memory leak in the Linux kernel tracing subsystem allows local attackers to cause denial of service by triggering histogram initialization failures.

- **Severity:** Not scored
- **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:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104586, BELL-CVE-2026-97923, DEBIAN-CVE-2026-97923, GHSA-28hv-8h97-8cx6, UBUNTU-CVE-2026-97923

## What is CVE-2026-97923?

CVE-2026-97923 is a memory corruption vulnerability in Linux, published on 25 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: Free histogram the var ref when its initialization fails

create_var_ref() allocates a VAR_REF hist_field and then calls
init_var_ref() to fill it in. When that fails the field is leaked.

commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy
var_refs") made destroy_hist_field() return early for
HIST_FIELD_FL_VAR_REF, since var refs are freed by walking the trigger's
var_refs[] array instead. create_var_ref() adds the field to that array
only after init_var_ref() has succeeded, so on this path the field is in
neither place and nothing frees it. The call was correct when it was
written, before var refs were taken out of destroy_hist_field().

init_var_ref() cannot free it either. The caller owns the field, so
init_var_ref() undoes only its own string allocations and leaves the
field alone. Freeing it there would leave create_var_ref() passing freed
memory to destroy_hist_field(), which reads its flags.

Call __destroy_hist_field(), which frees the field without consulting
the flag.

## Which versions are affected by CVE-2026-97923?


## How do I fix CVE-2026-97923?

Apply the vendor's patch.

## Is CVE-2026-97923 being exploited?

There is no known exploitation of CVE-2026-97923 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97923 and fix it if it is affected.

What it is: CVE-2026-97923 is a memory corruption vulnerability in Linux, published on 25 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-2026-97923 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-2026-97923/ (Markdown: https://insights.sbomify.com/CVE-2026-97923/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97923
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97923
- OSV: https://osv.dev/vulnerability/CVE-2026-97923

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97923/
Summaries are generated and may contain mistakes; the official description above is the record.