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

> An integer underflow in the iwlwifi driver causes out-of-bounds memory access when handling Block Ack sessions with a zero station mask, potentially leading to system crashes.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-93351, BELL-CVE-2026-64255, DEBIAN-CVE-2026-64255, GHSA-3prq-7cqf-r4ww, ROOT-OS-DEBIAN-13-CVE-2026-64255, ROOT-OS-UBUNTU-2204-CVE-2026-64255, UBUNTU-CVE-2026-64255

## What is CVE-2026-64255?

CVE-2026-64255 is a high-severity vulnerability in Linux kernel, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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().

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-64255?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64255?

Apply the vendor's patch.

## Is CVE-2026-64255 being exploited?

There is no known exploitation of CVE-2026-64255 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64255 and fix it if it is affected.

What it is: CVE-2026-64255 is a high-severity vulnerability in Linux kernel, published on 24 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64255 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64255/ (Markdown: https://insights.sbomify.com/CVE-2026-64255/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64255
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64255
- OSV: https://osv.dev/vulnerability/CVE-2026-64255

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64255/
Summaries are generated and may contain mistakes; the official description above is the record.