Microsoft has publicly acknowledged that its Azure Linux distribution is susceptible to CVE-2024-44987, a high-severity Linux kernel vulnerability that could give local attackers control over vulnerable systems. The advisory, released as part of Microsoft's new machine-readable vulnerability disclosure format, has sparked concern among users of other Microsoft products that rely on the Linux kernel, including Windows Subsystem for Linux 2 (WSL2) and Azure Kubernetes Service (AKS) nodes, which have not been explicitly declared safe.

What Is CVE-2024-44987?

CVE-2024-44987 is a use-after-free bug in the Linux kernel's IPv6 networking stack, specifically in the ip6_send_skb() function. Discovered by the syzbot kernel fuzzer and tracked publicly upstream, the flaw stems from a race condition where a network route object is accessed after being freed, potentially corrupting memory. An attacker with local access—a user account or the ability to run code on the machine—could exploit this to escalate privileges or cause system instability. Public scoring varies, but many sources place the base CVSS score around 7.8, marking it as high severity. The risk is limited by the local-access requirement, but in shared or multi-tenant environments, it remains a serious concern.

The Linux kernel community has released patches, and major distribution vendors—including Oracle Linux and Amazon Linux—have rolled out fixes for their kernel builds. The upstream fix ensures proper RCU read-lock handling to prevent the race.

Microsoft's Advisory and Its Scope

Microsoft's Security Response Center (MSRC) published a concise advisory for CVE-2024-44987. The key statement: "Azure Linux includes this open-source library and is therefore potentially affected." This is a direct attestation that Microsoft's Azure Linux images contain the vulnerable code. For customers running Azure Linux virtual machines, container images, or other instances, this is a clear call to apply updates.

However, the advisory does not say other Microsoft products are immune. Microsoft began publishing CSAF/VEX (Common Security Advisory Framework / Vulnerability Exploitability eXchange) documents in October 2025 to improve transparency for Azure Linux, and it stated that if impact to additional products is identified, it will update the CVE record. This phased rollout means many other Microsoft artifacts that ship Linux kernels—such as WSL2, AKS node images, and Azure Marketplace appliances—have not yet been inventoried or attested. The absence of a statement is not proof of safety.

Who Is Affected and What It Means for You

Home Users

Most home users are unlikely to run Azure Linux directly. The more common risk is through WSL2, which uses a Linux kernel distributed and updated by Microsoft. If you use WSL2 for development or casual tinkering, you may be running a kernel that has not been confirmed safe or fixed. At this time, Microsoft has not issued a statement about WSL2.

Power Users and Developers

Power users who run WSL2 or container workflows should check the kernel version with uname -r. If the version predates the upstream fix and you rely on IPv6 or multi-user workload separation, consider updating your WSL2 kernel via Windows Update or manual installation once a patched version is confirmed. For those building applications on Azure Linux base images, rebuild your containers with the latest patched images as soon as they are available.

IT Administrators

If your organization uses Azure Linux virtual machines, AKS clusters with Azure Linux node images, or any Azure Marketplace offerings built on Azure Linux, prioritize patching. Those systems are explicitly attested as affected. For other Linux-based Microsoft artifacts in your environment, perform an inventory:

  • Identify every Microsoft-supplied Linux kernel in use (WSL2, AKS nodes, VM images, container base images).
  • Check the kernel version and compare it against the upstream fix. Stable branches that include the patch are available from kernel.org, and distributions often publish their own advisories with version details.
  • If you cannot verify the fix, treat the system as potentially vulnerable until Microsoft provides an explicit "Not Affected" or "Fixed" attestation.

How We Got Here

The CVE was reported by syzbot in mid-2024 and rapidly fixed in the mainline kernel. The fix was backported to various stable kernel trees, and Linux distributors began issuing updates. Microsoft's own Azure Linux team, committed to keeping the distribution up to date, incorporated the patches and disseminated them through their normal update channels. Concurrently, Microsoft launched its CSAF/VEX transparency initiative, aiming to deliver machine-readable vulnerability data for Azure Linux. The blog post accompanying the rollout emphasized a priority on Azure Linux, with a promise to expand to other products over time.

This CVE is one of the first to receive a CSAF/VEX attestation from Microsoft, and the advisory reflects the initial scope of that program. For many customers, this marks a shift toward clearer, automatable vulnerability information—but the limited scope has also caused confusion.

Immediate Actions to Take

  1. Apply Azure Linux updates now. Microsoft's advisory confirms Azure Linux is affected; package updates have been released. Patch all Azure Linux instances, including virtual machines, container hosts, and base images.
  2. Audit your full Microsoft Linux footprint. Gather kernel versions from WSL2 instances, AKS nodes, Azure Stack HCI, and any marketplace images. For WSL2, you can run uname -r in the Linux terminal to get the kernel release.
  3. Cross-reference with upstream fixes. Visit the Linux kernel CVE annoucement archives or your distribution's advisory page to identify the version ranges that include the fix. For example, Oracle's ELSA advisory lists the minimal package versions that resolve the issue. If your kernel is older, assume it needs patching.
  4. Use automated scanning tools. Vulnerability scanners like Trivy, Snyk, or Microsoft's own container scanning solutions can detect outdated kernel packages. Ingest Microsoft's CSAF/VEX feeds (available through MSRC) to automate inventory checks as coverage expands.
  5. Apply temporary mitigations where patching is delayed. If you cannot immediately update a suspect kernel, restrict local access: minimize user accounts, limit SSH access, and ensure containers run with least privilege. Disabling IPv6 may reduce attack surface but is not a complete fix and may not be practical in all networks.
  6. Monitor MSRC for updates. Microsoft has stated it will update the CVE if more products are found to be affected. Keep an eye on the CVE page and subscribe to security notifications.

What to Watch Next

Microsoft's CSAF/VEX rollout will be a key bellwether. As the company extends the program, expect more definitive statements about WSL2, AKS, and other Linux-based services. Until then, the safest course is to assume any Microsoft-shipped Linux kernel could be vulnerable and to verify independently. The community will also watch whether other cloud vendors adopt similar attestation models, which could eventually streamline patch management across platforms.

CVE-2024-44987 is a reminder that shared upstream code demands shared responsibility. Microsoft's transparency is a welcome step, but it shifts the burden of verification to customers for products outside the initial attestation scope—at least for now.