# CVE-2026-31413: bpf: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR

> A logic error in the Linux kernel BPF verifier allows out-of-bounds map access, potentially leading to code execution or privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 12 Apr 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-31413, DEBIAN-CVE-2026-31413, GHSA-q7pg-xjgf-wr6f, ROOT-OS-UBUNTU-2404-CVE-2026-31413, UBUNTU-CVE-2026-31413

## What is CVE-2026-31413?

CVE-2026-31413 is a high-severity memory corruption vulnerability in Linux kernel, published on 12 Apr 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: Fix unsound scalar forking in maybe_fork_scalars() for BPF_OR

maybe_fork_scalars() is called for both BPF_AND and BPF_OR when the
source operand is a constant.  When dst has signed range [-1, 0], it
forks the verifier state: the pushed path gets dst = 0, the current
path gets dst = -1.

For BPF_AND this is correct: 0 & K == 0.
For BPF_OR this is wrong:    0 | K == K, not 0.

The pushed path therefore tracks dst as 0 when the runtime value is K,
producing an exploitable verifier/runtime divergence that allows
out-of-bounds map access.

Fix this by passing env->insn_idx (instead of env->insn_idx + 1) to
push_stack(), so the pushed path re-executes the ALU instruction with
dst = 0 and naturally computes the correct result for any opcode.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-31413?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31413?

Apply the vendor's patch.

## Is CVE-2026-31413 being exploited?

There is no known exploitation of CVE-2026-31413 in the wild and no public exploit code.

Public exploit code:

- CVE-2026-31413: BPF verifier soundness bug - container escape (github_poc): https://github.com/Rat5ak/CVE-2026-31413-BPF-Container-Escape

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31413 and fix it if it is affected.

What it is: CVE-2026-31413 is a high-severity memory corruption vulnerability in Linux kernel, published on 12 Apr 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-2026-31413 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31413/ (Markdown: https://insights.sbomify.com/CVE-2026-31413/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31413
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31413
- OSV: https://osv.dev/vulnerability/CVE-2026-31413

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31413/
Summaries are generated and may contain mistakes; the official description above is the record.