# CVE-2026-90195: riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args

> Missing sign-extension in RISC-V BPF JIT for small signed arguments causes incorrect behavior, potentially leading to logic errors or crashes.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90195, DEBIAN-CVE-2026-90195, GHSA-wm8w-4px2-2hp8, UBUNTU-CVE-2026-90195

## What is CVE-2026-90195?

CVE-2026-90195 is a vulnerability in Linux, published on 17 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:

riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args

On RV64, the ABI requires sign-extension for signed 1-byte and 2-byte kfunc
args. However, the RV64 JIT currently does not perform sign-extension for
such kfunc args.

Before commit 7ce090afbf72 ("bpf: Infer zext_dst based on static register
liveness analysis"), state pruning could potentially omit zero-extension
of 32-bit subregisters, which inadvertently masked the above issue by making
the args appear as if they had been properly sign-extended. After that
commit, the problem is exposed, causing the kfunc_call/kfunc_call_test4
selftest to fail.

Fix this by extending the existing sign-extension logic to handle signed
1-byte and 2-byte kfunc args as well.

## Which versions are affected by CVE-2026-90195?


## How do I fix CVE-2026-90195?

Apply the vendor's patch.

## Is CVE-2026-90195 being exploited?

There is no known exploitation of CVE-2026-90195 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90195 and fix it if it is affected.

What it is: CVE-2026-90195 is a vulnerability in Linux, published on 17 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-2026-90195 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-2026-90195/ (Markdown: https://insights.sbomify.com/CVE-2026-90195/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90195
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90195
- OSV: https://osv.dev/vulnerability/CVE-2026-90195

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90195/
Summaries are generated and may contain mistakes; the official description above is the record.