# CVE-2026-72428: bpf: Fix stack slot index in nospec checks

> A flaw in Linux kernel BPF nospec checks allows bypassing Spectre v4 sanitization, potentially exposing sensitive data to local attackers.

- **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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72428, DEBIAN-CVE-2026-72428, GHSA-xwq5-6xrg-83hr, UBUNTU-CVE-2026-72428

## What is CVE-2026-72428?

CVE-2026-72428 is a vulnerability in Linux, published on 15 Aug 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 stack slot index in nospec checks

check_stack_write_fixed_off() computes the byte slot for a fixed-offset
stack write as -off - 1, and records each written byte in slot_type[] with
(slot - i) % BPF_REG_SIZE.

The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a
4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the
pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates
bytes 7..4. That can leave the second half-slot write without nospec_result
even though the bytes being overwritten still require sanitization.

Use the same slot index in the sanitization pre-check that the write path uses
when updating slot_type[].

## Which versions are affected by CVE-2026-72428?


## How do I fix CVE-2026-72428?

Apply the vendor's patch.

## Is CVE-2026-72428 being exploited?

There is no known exploitation of CVE-2026-72428 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72428 and fix it if it is affected.

What it is: CVE-2026-72428 is a vulnerability in Linux, published on 15 Aug 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-2026-72428 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-2026-72428/ (Markdown: https://insights.sbomify.com/CVE-2026-72428/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72428
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72428
- OSV: https://osv.dev/vulnerability/CVE-2026-72428

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72428/
Summaries are generated and may contain mistakes; the official description above is the record.