# CVE-2026-31696: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

> An unprivileged user can trigger a kernel warning and potential denial of service by providing an invalid ticket length in the rxrpc subsystem.

- **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:** 1 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-85433, BELL-CVE-2026-31696, DEBIAN-CVE-2026-31696, GHSA-jrvq-m3v6-8wm9, ROOT-OS-DEBIAN-11-CVE-2026-31696, ROOT-OS-DEBIAN-12-CVE-2026-31696, ROOT-OS-UBUNTU-2204-CVE-2026-31696, ROOT-OS-UBUNTU-2404-CVE-2026-31696, UBUNTU-CVE-2026-31696

## What is CVE-2026-31696?

CVE-2026-31696 is a high-severity vulnerability in Linux kernel, published on 1 May 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:

rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

In rxrpc_preparse(), there are two paths for parsing key payloads: the
XDR path (for large payloads) and the non-XDR path (for payloads <= 28
bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly
validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR
path fails to do so.

This allows an unprivileged user to provide a very large ticket length.
When this key is later read via rxrpc_read(), the total
token size (toksize) calculation results in a value that exceeds
AFSTOKEN_LENGTH_MAX, triggering a WARN_ON().

[ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc]

Fix this by adding a check in the non-XDR parsing path of rxrpc_preparse()
to ensure the ticket length does not exceed AFSTOKEN_RK_TIX_MAX,
bringing it into parity with the XDR parsing logic.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-31696?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31696?

Apply the vendor's patch.

## Is CVE-2026-31696 being exploited?

There is no known exploitation of CVE-2026-31696 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-2026-31696 and fix it if it is affected.

What it is: CVE-2026-31696 is a high-severity vulnerability in Linux kernel, published on 1 May 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-2026-31696 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-2026-31696/ (Markdown: https://insights.sbomify.com/CVE-2026-31696/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31696
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31696
- OSV: https://osv.dev/vulnerability/CVE-2026-31696

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31696/
Summaries are generated and may contain mistakes; the official description above is the record.