# CVE-2026-31635: rxrpc: fix oversized RESPONSE authenticator length check

> An attacker can cause a kernel crash by sending oversized rxrpc RESPONSE authenticators due to an inverted length check.

- **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-2026-31635, DEBIAN-CVE-2026-31635, GHSA-f5xm-f2m7-vrg6, UBUNTU-CVE-2026-31635

## What is CVE-2026-31635?

CVE-2026-31635 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 oversized RESPONSE authenticator length check

rxgk_verify_response() decodes auth_len from the packet and is supposed
to verify that it fits in the remaining bytes. The existing check is
inverted, so oversized RESPONSE authenticators are accepted and passed
to rxgk_decrypt_skb(), which can later reach skb_to_sgvec() with an
impossible length and hit BUG_ON(len).

Decoded from the original latest-net reproduction logs with
scripts/decode_stacktrace.sh:

RIP: __skb_to_sgvec()
  [net/core/skbuff.c:5285 (discriminator 1)]
Call Trace:
 skb_to_sgvec() [net/core/skbuff.c:5305]
 rxgk_decrypt_skb() [net/rxrpc/rxgk_common.h:81]
 rxgk_verify_response() [net/rxrpc/rxgk.c:1268]
 rxrpc_process_connection()
   [net/rxrpc/conn_event.c:266 net/rxrpc/conn_event.c:364
    net/rxrpc/conn_event.c:386]
 process_one_work() [kernel/workqueue.c:3281]
 worker_thread()
   [kernel/workqueue.c:3353 kernel/workqueue.c:3440]
 kthread() [kernel/kthread.c:436]
 ret_from_fork() [arch/x86/kernel/process.c:164]

Reject authenticator lengths that exceed the remaining packet payload.

Weakness: CWE-130 (Improper Handling of Length Parameter Inconsistency)

## Which versions are affected by CVE-2026-31635?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31635?

Apply the vendor's patch.

## Is CVE-2026-31635 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31635 exists.

Public exploit code:

- CVE-2026-31635 (github_poc): https://github.com/0xredash/CVE-2026-31635
- https://github.com/0xFuffM3/CVE-2026-31635-DirtyDecrypt (github_poc): https://github.com/0xFuffM3/CVE-2026-31635-DirtyDecrypt
- A Go implementation of dirtydecrypt (CVE-2026-31635) (github_poc): https://github.com/Koshmare-Blossom/DirtyDecrypt-go

## 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-2026-31635 and fix it if it is affected.

What it is: CVE-2026-31635 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-31635 exists.

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-2026-31635/ (Markdown: https://insights.sbomify.com/CVE-2026-31635/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31635
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31635
- OSV: https://osv.dev/vulnerability/CVE-2026-31635

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31635/
Summaries are generated and may contain mistakes; the official description above is the record.