# CVE-2026-31640: rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

> A logic error in the Linux kernel's rxrpc module causes incorrect packet handling, potentially leading to memory leaks and denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Apr 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-31640, DEBIAN-CVE-2026-31640, GHSA-gwvh-rgq7-hjcw, UBUNTU-CVE-2026-31640

## What is CVE-2026-31640?

CVE-2026-31640 is a high-severity vulnerability in Linux kernel, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: Fix use of wrong skb when comparing queued RESP challenge serial

In rxrpc_post_response(), the code should be comparing the challenge serial
number from the cached response before deciding to switch to a newer
response, but looks at the newer packet private data instead, rendering the
comparison always false.

Fix this by switching to look at the older packet.

Fix further[1] to substitute the new packet in place of the old one if
newer and also to release whichever we don't use.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-31640?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31640?

Apply the vendor's patch.

## Is CVE-2026-31640 being exploited?

There is no known exploitation of CVE-2026-31640 in the wild and no public exploit code.

## 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-2026-31640 and fix it if it is affected.

What it is: CVE-2026-31640 is a high-severity vulnerability in Linux kernel, published on 24 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31640 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-2026-31640/ (Markdown: https://insights.sbomify.com/CVE-2026-31640/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31640
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31640
- OSV: https://osv.dev/vulnerability/CVE-2026-31640

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31640/
Summaries are generated and may contain mistakes; the official description above is the record.