Microsoft this week confirmed that its Azure Linux distribution contains a vulnerable open-source wireless driver component, while leaving the door open to the possibility that other Microsoft products might also be affected. The advisory, posted to the Microsoft Security Response Center (MSRC), addresses public questions around CVE-2025-37976, a kernel-level flaw in the ath12k Wi-Fi driver that was later marked as rejected by its assigning authority. The company's message to system administrators: Azure Linux is the only product Microsoft has formally attested as containing the code, but the absence of attestations for other products is not proof they are safe.

What Microsoft disclosed

The MSRC advisory responds directly to a single question: "Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability?" Microsoft's answer, while brief, carries a lot of weight for anyone managing a fleet of Microsoft-supplied Linux images.

"One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed," the advisory reads. "Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025."

Then comes the crucial part: "If impact to additional products is identified, we will update the CVE to reflect this."

Read between the lines: Microsoft is saying that Azure Linux is the product they have validated as containing the vulnerable component, but they are not claiming that no other Microsoft-distributed image, kernel, or appliance could be affected. They are promising to update their public vulnerability advisories if further products are found to be impacted.

The vulnerability: A brief timeline

The root cause lies in a change to the Linux kernel's ath12k driver—a driver for Qualcomm Wi-Fi hardware. In April 2025, a patch was committed upstream to fix an improper ring entry fetch in the ath12k_dp_mon_srng_process function. The fix was then backported to stable kernel branches, but at least one backport had a mistake that required a revert and a corrected version.

By late May 2025, CVE-2025-37976 appeared in public databases to track this issue. However, on June 18, 2025, the CVE Numbering Authority (CNA) rejected or withdrew that identifier. This administrative action created confusion: some scanners began dropping the alert, while other vendors assigned different CVE IDs or tracked the commit directly.

Microsoft's move to publish machine-readable vulnerability disclosures in the Common Security Advisory Framework (CSAF) format and Vulnerability Exploitability eXchange (VEX) statements, beginning in October 2025, was partly meant to cut through such noise. By providing per-product attestations, Microsoft aims to give operators a clear "affected" or "not affected" signal for the artifacts it ships.

What the attestation actually means for you

Microsoft's VEX statement for CVE-2025-37976 is a positive confirmation: Azure Linux images include the ath12k code and are potentially vulnerable. That's actionable—Azure Linux users should patch immediately.

But many organizations run other Microsoft-provided Linux artifacts. These include:

  • Azure Marketplace VM images
  • Windows Subsystem for Linux 2 (WSL2) kernels
  • Azure Kubernetes Service (AKS) node images
  • Azure IoT device images
  • Container images used in various Azure services
  • Specialized kernels for appliances like Azure Bastion

None of these have an explicit VEX attestation for CVE-2025-37976. The absence of an attestation is not a guarantee of safety—it simply means Microsoft hasn't yet said anything about those products.

Why might other products contain the same code? The answer is technical. The ath12k driver's presence depends on kernel version, included commits, compile-time configuration (like CONFIG_ATH12K), whether it's built as a module or built-in, and the hardware profile of the image. Cloud images often omit wireless drivers, but consumer or edge device images might include them. WSL2 kernels, for instance, have their own configuration that could enable the driver.

How to check if your systems are vulnerable

Instead of waiting for Microsoft to expand its attestations, security teams should verify the presence of the ath12k code directly on any Microsoft-sourced Linux system. The following checks can be scripted and automated for large environments.

1. Identify the kernel version

Run uname -a or inspect /proc/version. Look for build strings that hint at a Microsoft-supplied kernel (e.g., containing "azure" or "WSL").

2. Check kernel configuration for ath12k

Search /boot/config-$(uname -r) or /proc/config.gz for CONFIG_ATH12K. If this option is not set, the driver was not compiled in.

3. Look for the module on the filesystem

  • Check if the module is loaded: lsmod | grep ath12k
  • Search for the module files: find /lib/modules/$(uname -r) -name 'ath12k*'
  • If found, inspect module info: modinfo <path-to-ath12k.ko>

4. Examine kernel source packages or changelogs

If you have access to the source tree of the kernel image, search for the function names involved in the upstream fix: ath12k_dp_mon_srng_process, ath12k_hal_srng_src_get_next_entry, ath12k_hal_srng_dst_get_next_entry. Their presence indicates the driver code is included.

5. For containers and images

Extract image layers and inspect /lib/modules and /boot. Keep in mind that container-based vulnerability scans often misattribute kernel CVEs because they check source packages rather than actual kernel modules. The host kernel is the real vector for many driver flaws.

If any of these checks return positive, you have work to do.

Mitigation steps

The best mitigation is to apply a vendor-supplied patch that includes the corrected code. For Azure Linux, Microsoft has released updates for its attested images—apply those immediately.

If a patch isn't yet available for your specific product, or if you simply don't need Wi-Fi driver support, you can reduce risk:

  • Blacklist the module: Add blacklist ath12k to a file in /etc/modprobe.d/ and rebuild the initramfs. This prevents the driver from loading, though the code remains on disk.
  • Remove the module physically (with caution): If you maintain custom images, you can remove the ath12k kernel module files and rebuild. However, this may cause issues if future updates restore them.
  • Apply access controls: Restrict local user accounts and limit the ability to load kernel modules. Use SELinux or AppArmor to contain processes, and enable kernel lockdown features where possible.
  • Network segmentation: Since this is a local driver flaw, ensure that hosts are not directly exposed to untrusted networks unnecessarily.
  • Immutable infrastructure: If you use CI/CD pipelines, rebuild your images from a patched base and redeploy.

Always test any kernel changes in a staging environment first, especially if you're removing modules.

What the CVE rejection means for vulnerability management

The "Rejected" or "Withdrawn" status of CVE-2025-37976 is an administrative detail, not a technical retraction of the flaw. The CNA may have withdrawn the identifier because of duplication or misassignment, but the underlying kernel fix and the backporting mistakes remain real.

For vulnerability scanners, this creates a headache. Some may stop flagging the CVE altogether, leading to false negatives. Others may use a different identifier, causing duplicate alerts. The only reliable way to know is to use artifact-level checks, not just CVE-ID-based scans.

Microsoft's move to CSAF/VEX helps, but only for the products it covers. Organizations should update their vulnerability management workflows to prioritize package- and module-level verification for kernel issues, especially when CVE metadata is in flux.

The bottom line

Microsoft's advisory gives Azure Linux customers a clear action item: patch now. For everyone else running Microsoft-supplied Linux kernels—from WSL2 workstations to AKS nodes—the answer is less clear. Don't assume you're safe just because there's no VEX statement. Check your systems for the ath12k driver, and if you find it, take steps to mitigate or patch.

Keep an eye on the MSRC page for updates. Microsoft has promised to expand its VEX coverage over time, and new attestations could appear as they validate more products. In the meantime, inventory your Microsoft Linux artifacts and automate these checks—your security depends on knowing what code is actually running, not just what a scanner says.