# CVE-2026-97922: tracing: Free histogram var refs regardless of how often they are referenced

> A memory leak in Linux kernel histogram triggers allows local attackers to exhaust memory by removing triggers with multiple variable references.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **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-104196, BELL-CVE-2026-97922, DEBIAN-CVE-2026-97922, GHSA-m6gp-f257-gxcp, UBUNTU-CVE-2026-97922

## What is CVE-2026-97922?

CVE-2026-97922 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 var refs regardless of how often they are referenced

Using the same variable three or more times in one hist trigger leaks the
variable reference and its strings when the trigger is removed.

commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy
var_refs") made a trigger's var_refs[] array the only owner of a var ref:
destroy_hist_field() returns early for HIST_FIELD_FL_VAR_REF, so the field
expressions never destroy one. One entry, freed once, no count needed.

commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same
var as value") then made repeated references share one object and added a
count of them. Only the increment side exists, since those expressions
still return early and never drop a reference, so __destroy_hist_field()
sees how many references were created rather than how many are left. It
frees when the decremented count is 0 or 1, so two references work and
three or more leak.

Sharing kept one array entry per object, and create_var_ref() searches and
appends within a single trigger, so nothing outside it holds the object.
Removing a trigger whose variables are still referenced is already refused
by check_var_refs() with -EBUSY. Drop the count and free unconditionally.

## Which versions are affected by CVE-2026-97922?


## How do I fix CVE-2026-97922?

Apply the vendor's patch.

## Is CVE-2026-97922 being exploited?

There is no known exploitation of CVE-2026-97922 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97922 and fix it if it is affected.

What it is: CVE-2026-97922 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-2026-97922 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-2026-97922/ (Markdown: https://insights.sbomify.com/CVE-2026-97922/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97922
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97922
- OSV: https://osv.dev/vulnerability/CVE-2026-97922

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97922/
Summaries are generated and may contain mistakes; the official description above is the record.