# CVE-2026-98033: bpf: Preserve inner map identity in callback frames

> A use-after-free vulnerability in the Linux kernel BPF subsystem allows local attackers to execute arbitrary code or escalate privileges via timer callbacks.

- **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:** 21 Oct 2026
- **Also known as:** AZL-104549, BELL-CVE-2026-98033, DEBIAN-CVE-2026-98033, GHSA-4746-9qhc-mc6f, UBUNTU-CVE-2026-98033

## What is CVE-2026-98033?

CVE-2026-98033 is an use after free 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:

bpf: Preserve inner map identity in callback frames

Callback frame constructors initialize map-typed argument registers with
__mark_reg_known_zero() and then restore map_ptr. This clears map_uid,
which is the only field distinguishing inner maps that share an
inner_map_meta template.

When a timer callback invokes bpf_for_each_map_elem() on a second inner
map, both the saved first map and the second map value can reach the nested
callback as the same template with map_uid zero. bpf_timer_init() then
accepts pairing the timer from the second map with the first map.

The runtime records the first map in the timer without taking a reference.
Freeing that map does not find the timer stored in the second map, so a
later timer callback dereferences the freed map.

Copy map_uid from the same caller register as map_ptr when constructing
for-each, timer/workqueue, and task-work callback arguments. The existing
identity check can then reject mismatched inner maps while allowing a
callback value to be paired with its actual map.

## Which versions are affected by CVE-2026-98033?


## How do I fix CVE-2026-98033?

Apply the vendor's patch.

## Is CVE-2026-98033 being exploited?

There is no known exploitation of CVE-2026-98033 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98033 and fix it if it is affected.

What it is: CVE-2026-98033 is an use after free 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-2026-98033 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-2026-98033/ (Markdown: https://insights.sbomify.com/CVE-2026-98033/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98033
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98033
- OSV: https://osv.dev/vulnerability/CVE-2026-98033

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98033/
Summaries are generated and may contain mistakes; the official description above is the record.