# CVE-2026-98039: bpf: Require MEM_PERCPU for percpu kptr stores

> A flaw in the Linux kernel BPF subsystem allows arbitrary kernel read/write and potential privilege escalation by bypassing per-CPU pointer type checks.

- **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:** BELL-CVE-2026-98039, DEBIAN-CVE-2026-98039, GHSA-hqcj-5pcp-63q5, UBUNTU-CVE-2026-98039

## What is CVE-2026-98039?

CVE-2026-98039 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:

bpf: Require MEM_PERCPU for percpu kptr stores

map_kptr_match_type() treats perm_flags as the set of register type flags
that a kptr field permits. Adding MEM_PERCPU to that set for
BPF_KPTR_PERCPU does not require the source register to carry it, however.
The subset test consequently accepts both a plain bpf_obj_new() allocation
and a referenced kernel pointer into a __percpu_kptr map field.

Loads from the field are always marked MEM_PERCPU. Consumers then treat the
stored value as the cookie returned by bpf_percpu_obj_new(): per-CPU pointer
helpers relocate it, and map teardown selects the per-CPU free path. A plain
allocation can therefore provide an arbitrary kernel read/write, while a
kernel pointer can be relocated into an invalid address or sent through a
missing destructor.

Require the source MEM_PERCPU flag to match the destination field kind.
This preserves valid bpf_percpu_obj_new() stores and rejects both the
program-BTF and kernel-BTF variants.

## Which versions are affected by CVE-2026-98039?


## How do I fix CVE-2026-98039?

Apply the vendor's patch.

## Is CVE-2026-98039 being exploited?

There is no known exploitation of CVE-2026-98039 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98039 and fix it if it is affected.

What it is: CVE-2026-98039 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-2026-98039 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-2026-98039/ (Markdown: https://insights.sbomify.com/CVE-2026-98039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98039
- OSV: https://osv.dev/vulnerability/CVE-2026-98039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98039/
Summaries are generated and may contain mistakes; the official description above is the record.