CVE-2025-39746 — a Linux kernel fix for the ath10k Wi‑Fi driver that tells the driver to shut down when hardware looks unreliable — has drawn attention not only because it affects common Qualcomm Atheros chipsets, but because Microsoft’s public vulnerability attestation named Azure Linux as a product that “includes this open‑source library and is therefore potentially affected.” That wording has prompted a practical question for administrators and security teams: is Azure Linux the only Microsoft product that ships the vulnerable component, or should other Microsoft images and artifacts in your estate be considered in scope? The short, evidence‑based answer is: Azure Linux is the only Microsoft product Microsoft has publicly attested as affected so far, but it is not technically the only Microsoft artifact that could include the vulnerable code; other Microsoft‑supplied kernels and images may include the same upstream driver depending on build configuration and packaging choices.
Background / Overview
CVE‑2025‑39746 is a kernel‑level robustness fix that targets the ath10k driver stack used with Qualcomm Atheros Wi‑Fi chipsets. The upstream kernel description and multiple downstream trackers summarize the root issue plainly: under certain rare conditions the driver can lose its PCIe connectivity or repeatedly restart the hardware, causing WMI command timeouts and a watchdog‑driven failure path that can escalate to a system panic during resume sequences. The upstream remedy is defensive: detect repeated recovery failures, treat the hardware as unreliable, and stop attempting further ath10k operations to avoid a catastrophic watchdog timeout. Security trackers from several distributions and vendors recorded the same facts and mapped the kernel stable commits into packaged fixes. Ubuntu and Debian published advisories describing the behavioral symptoms and the remediation paths applied to their kernel packages; distributions have been shipping patched kernels that incorporate the upstream change. What this means in practical terms is that the vulnerability primarily impacts Linux kernels that include the ath10k driver for the affected Qualcomm devices. The immediate operational impact is availability and reliability — noisy kernel logs, device restart loops, and in the worst observed interleavings, resume‑time panics — rather than a straightforward remote code execution vector. Even so, the severity depends on the deployment context (multi‑tenant clouds, automated CI runners, or embedded devices that cannot be rebooted safely are higher risk).What Microsoft actually published, and how to read it
Microsoft’s public advisory language (as reflected in the MSRC update guide attestation) states that Azure Linux “includes this open‑source library and is therefore potentially affected”, and that Microsoft has committed to publishing machine‑readable CSAF/VEX attestations and updating CVE records if additional Microsoft products are found to ship the component. That language is a product‑scope attestation: it documents what Microsoft has validated to date for a particular product family (Azure Linux) and is not an explicit denial that other Microsoft products might include the same upstream code.Microsoft’s phrasing is procedural and consistent with industry practice: large vendors often start VEX/CSAF publication with a limited set of product families where inventory and SBOM work is complete, then expand coverage as they validate additional images, kernels, and packages. Treat the attestation as an authoritative “yes” for Azure Linux and as a work in progress for other Microsoft artifacts.
Why the answer is “No — not necessarily the only Microsoft product”
It’s tempting to read the MSRC sentence as a blanket statement about all Microsoft technology, but three technical realities change the interpretation:- Kernel code presence is a build‑time property. Whether a particular kernel contains ath10k or the wireless stack (cfg80211/mac80211) is determined by how that kernel was configured and built (kernel config flags such as CONFIG_ATH10K, CONFIG_CFG80211, or whether ath10k was built as a module or compiled in). Microsoft ships multiple kernel artifacts that may be configured differently.
- Microsoft ships multiple, distinct Linux kernel artifacts and images. Examples include the linux‑azure kernels used for some Azure VM images, curated Azure Linux distributions, Marketplace images, and the WSL2 kernel that Microsoft publishes on GitHub. Each of those is a separate artifact and may have different kernel configs and module sets. If any of those artifacts include ath10k (or cfg80211/mac80211 code paths that touch the same problem area), they could be affected.
- Many third‑party Linux distributions and partner images available in Azure also ship cfg80211 and ath10k as part of their kernels. Those images are independently maintained by their vendors (Canonical, Red Hat, SUSE, OEMs) and are therefore in scope from a customer‑impact perspective even if Microsoft’s internal product attestation initially focused on Azure Linux.
Where else to look inside a Microsoft environment
Administrators should treat this as a question of artifact provenance and configuration. The following Microsoft artifacts are logical places to check:- Azure Linux (confirmed) — Microsoft has published a VEX/CSAF attestation and stated Azure Linux includes the relevant open‑source component. Treat this product’s inventory as authoritative for Azure Linux images.
- linux‑azure / Azure VM kernels — Azure uses specialized kernel builds for VM images; those kernel packages may include cfg80211 or ath10k depending on configuration. Check linux‑azure package changelogs and the specific image you run.
- WSL2 kernel (Windows Subsystem for Linux) — WSL2 uses a Microsoft‑published kernel (WSL2‑Linux‑Kernel) on GitHub; that kernel’s configuration determines whether ath10k or related wireless subsystems are present. WSL kernels are buildable and modifiable by users, so the default WSL kernel may differ from custom WSL kernels deployed by power users.
- Azure Marketplace and curated container images — images published by Microsoft partners or third parties may ship kernels of their own; verify the image vendor’s advisories and package changelogs.
- Managed services and runtimes — some managed offerings (for example, curated machine learning or big data runtimes) may include baked‑in Linux images; validate the runtime images you consume.
- IoT/Edge/Embedded appliances — Microsoft‑branded or partner appliances that run a Linux userland with a vendor kernel may contain ath10k if the hardware requires it; vendor backport cadence matters here.
Practical verification checklist (what to run now)
Verify a host or image quickly with these steps. These are standard, low‑risk checks you can run as root or with appropriate admin privileges.- Identify whether ath10k is present and loaded on a running host:
- lsmod | grep -i ath10k
- dmesg | grep -i ath10k
- Inspect kernel configuration for wireless stack flags:
- zcat /proc/config.gz | grep -E 'CONFIG_CFG80211|CONFIG_ATH10K|CONFIG_MAC80211'
- grep -E 'CONFIG_CFG80211|CONFIG_ATH10K' /boot/config-$(uname -r)
- If you run WSL2, check the WSL kernel config repo and your local ~/.wslconfig if you use a custom kernel:
- Review the Microsoft/WSL2‑Linux‑Kernel repo for the active config used in your WSL release.
- For Azure VM images, inspect the image’s kernel package changelog and distro CVE tracker:
- apt changelog linux-image-$(uname -r) (Debian/Ubuntu)
- rpm -q --changelog kernel | grep CVE-2025-39746 (RHEL/SUSE)
- Centralize inventory: feed results into your asset management / CMDB so you can correlate which images and VMs run kernels that include ath10k or cfg80211.
Recommended mitigations and remediation path
- Apply vendor/distro kernel updates that include the upstream patch as soon as possible. Distro security centers (Ubuntu, Debian, Red Hat) and cloud provider advisories list the patched package versions. Reboot hosts into the updated kernel to ensure the fix is active.
- For Microsoft‑published artifacts:
- If you use Azure Linux, follow Microsoft’s VEX/CSAF attestation and the Azure Linux update guidance first (Microsoft has explicitly listed Azure Linux as potentially affected).
- For WSL2 users, install the latest WSL kernel updates from Microsoft and, if you run a custom WSL kernel, ensure your config does not build in the vulnerable driver or that you have merged the stable upstream commit.
- If patching is delayed or impractical on certain hosts:
- Blacklist the ath10k module on systems that do not require the hardware: echo "blacklist ath10k_pci" > /etc/modprobe.d/blacklist-ath10k.conf and rebuild initramfs where necessary.
- Isolate affected hosts from untrusted local actors; restrict who can trigger driver operations or device‑simulate interfaces that might exercise the failure path.
- Increase kernel log aggregation and monitoring to detect the specific watchdog/WMI timeout traces described in the CVE (search for the diagnostic snippets in dmesg/journalctl).
Severity, exploitability and operational risk — cross‑checked evidence
Multiple independent trackers characterize CVE‑2025‑39746 as a reliability/availability issue with tangible operational impact in certain environments. The NVD and OSV entries describe the kernel crash/resume symptoms and point to the upstream patch; Ubuntu and Amazon ALAS assigned medium‑to‑important priorities for the images they track. Different trackers may compute numeric scores differently, but the operational reality is consistent: this bug can cause host instability, and that matters more in automated, multi‑tenant, or critical infrastructure settings than in an isolated desktop. Two‑source cross‑check (examples):- The upstream description and commits on the kernel stable tree show the implemented defensive threshold and logic change to consider the hardware unreliable after repeated retries.
- Distribution advisories (Ubuntu/Debian) and cloud trackers (ALAS/AWS) map the fix into packaged kernels and provide pragmatic guidance for image owners to upgrade and reboot.
Critical analysis — strengths and potential risks of Microsoft’s attestation approach
Strengths- Transparency and automation: Microsoft’s move to publish CSAF/VEX for Azure Linux and to assert product‑level attestations is a positive step for automation and clarity. Customers running Azure Linux can immediately use the VEX/CSAF outputs to drive detection and remediation.
- Practical scope control: Starting VEX publication with one product family (Azure Linux) makes the attestation work tractable. It gives customers a verified signal they can automate against, reducing the immediate triage load for that product family.
- Alignment with distro fixes: Microsoft’s advisory model aligns with upstream kernel and distro packaging, which is the correct engineering path for kernel CVEs: accept a small defensive patch upstream, distribute via distro/kernel packages, and require reboots to effect the remediation.
- Phased coverage leaves a verification gap. Microsoft’s attestation for Azure Linux confirms that product only; customers who rely on other Microsoft images (WSL, Marketplace images, linux‑azure kernels, curated managed runtimes) must verify each artifact individually. That creates potential blind spots if organizations assume a single attestation covers all Microsoft‑branded artifacts.
- Build‑time variability complicates mass claims. The presence of kernel subsystems depends on kernel configuration. Even within Microsoft’s own artifacts, different kernel builds and product channels may enable or disable the wireless stack. That means a “Microsoft‑branded” kernel is not a binary yes/no — it’s an artifact‑level question.
- Vendor backport lag outside mainstream images. Embedded and partner images often lag upstream fixes. Organizations that run long‑lived OEM images or vendor forks must track vendor advisories actively rather than relying on public VEX attestations for Azure Linux alone.
Recommended operational playbook (quick steps for sysadmins)
- Inventory: enumerate all running Linux kernels in your estate (VMs, containers with privileged kernels, WSL instances, appliances).
- Detect: scan for ath10k/cfg80211 presence using lsmod and kernel config queries. Aggregate results into your patch tracker.
- Patch: prioritize nodes where ath10k is present and where availability matters — apply distro/kernel vendor updates and reboot.
- Validate: confirm the kernel package changelog includes the upstream commit or CVE tag, and verify post‑patch logs no longer show the WMI/watchdog timeout traces.
- Isolate / compensate: for devices that cannot be patched quickly, blacklist modules or add network/isolation controls to reduce the operational exposure window.
- Monitor: add kernel log rules for the specific warning/trace text described in the CVE so you catch symptomatic hosts quickly.
Conclusion
Microsoft’s public attestation that Azure Linux includes the open‑source library and is therefore potentially affected is accurate and useful — it gives Azure Linux customers a verifiable, machine‑readable VEX/CSAF signal to automate against. However, that attestation is product‑scoped, not a universal statement about every Microsoft image or kernel artifact. Because kernel components like ath10k and the wireless stack are included or omitted at build time, other Microsoft‑distributed kernels (linux‑azure, WSL2 kernels, Marketplace images) and partner/vendor images could also include the vulnerable code depending on how they were configured and packaged. Customers must therefore treat the Azure Linux attestation as an authoritative yes for that product and perform artifact‑level verification — inventory, module checks, package changelog validation, and targeted patching — across all Microsoft images they run.In operational terms: prioritize patch‑and‑reboot for any host that runs ath10k or the wireless kernel subsystems, automate inventory checks against Microsoft’s CSAF/VEX outputs where available, and do not assume a single attestation covers all Microsoft‑supplied artifacts in your environment. The technical fix is small and straightforward at the kernel level; the real work is ensuring every distinct artifact and vendor image in your estate is validated and patched.
Source: MSRC Security Update Guide - Microsoft Security Response Center
