# CVE-2026-98631: xsk: Use a 32-bit compare in xsk_map_gen_lookup

> A sign-extension flaw in Linux kernel XSK map lookup allows out-of-bounds memory reads, potentially causing information disclosure 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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108740, BELL-CVE-2026-98631, DEBIAN-CVE-2026-98631, GHSA-r8m8-f9qq-5h53, UBUNTU-CVE-2026-98631

## What is CVE-2026-98631?

CVE-2026-98631 is a vulnerability in Linux, published on 18 Oct 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:

xsk: Use a 32-bit compare in xsk_map_gen_lookup

xsk_map_gen_lookup() loads a u32 key and compares it with max_entries
using BPF_JMP_IMM. BPF immediates are sign-extended to 64 bits, so a
max_entries value of 0x80000000 or higher becomes a threshold larger
than every zero-extended 32-bit key. An out-of-range index then skips
the bounds check and the generated lookup reads past xsk_map[].

Compare with BPF_JMP32_IMM so the check stays in 32-bit unsigned range.

## Which versions are affected by CVE-2026-98631?


## How do I fix CVE-2026-98631?

Apply the vendor's patch.

## Is CVE-2026-98631 being exploited?

There is no known exploitation of CVE-2026-98631 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98631 and fix it if it is affected.

What it is: CVE-2026-98631 is a vulnerability in Linux, published on 18 Oct 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-2026-98631 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-2026-98631/ (Markdown: https://insights.sbomify.com/CVE-2026-98631/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98631
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98631
- OSV: https://osv.dev/vulnerability/CVE-2026-98631

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98631/
Summaries are generated and may contain mistakes; the official description above is the record.