# CVE-2026-31638: rxrpc: Only put the call ref if one was acquired

> A null pointer dereference in the Linux kernel's rxrpc module allows remote attackers to cause a system crash via crafted packets.

- **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:** 19 Oct 2026
- **Also known as:** AZL-83672, BELL-CVE-2026-31638, DEBIAN-CVE-2026-31638, GHSA-5vqj-w88j-2624, ROOT-OS-DEBIAN-13-CVE-2026-31638, ROOT-OS-UBUNTU-2404-CVE-2026-31638, UBUNTU-CVE-2026-31638

## What is CVE-2026-31638?

CVE-2026-31638 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: Only put the call ref if one was acquired

rxrpc_input_packet_on_conn() can process a to-client packet after the
current client call on the channel has already been torn down.  In that
case chan->call is NULL, rxrpc_try_get_call() returns NULL and there is
no reference to drop.

The client-side implicit-end error path does not account for that and
unconditionally calls rxrpc_put_call().  This turns a protocol error
path into a kernel crash instead of rejecting the packet.

Only drop the call reference if one was actually acquired.  Keep the
existing protocol error handling unchanged.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-31638?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31638?

Apply the vendor's patch.

## Is CVE-2026-31638 being exploited?

There is no known exploitation of CVE-2026-31638 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-2026-31638 and fix it if it is affected.

What it is: CVE-2026-31638 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-2026-31638 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-2026-31638/ (Markdown: https://insights.sbomify.com/CVE-2026-31638/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31638
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31638
- OSV: https://osv.dev/vulnerability/CVE-2026-31638

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31638/
Summaries are generated and may contain mistakes; the official description above is the record.