Azure Linux Attestation: CVE-2024-39474 and Product Scope

A carefully scoped upstream fix for a Linux kernel memory-allocation bug—tracked as CVE-2024-39474—has rekindled an operational question many administrators ask when a vendor publishes a product-scoped vulnerability attestation: when Microsoft says “Azure Linux includes this open‑source library and is therefore potentially affected,” does that mean only Azure Linux ships the vulnerable code?

Background​

CVE-2024-39474 is a bug in the Linux kernel's vmalloc/kvmalloc pathway where a change to support the GFP_NOFAIL behavior conflicted with earlier logic that causes vmalloc to back off when the current task is being OOM‑killed. The practical result: under a particular sequence (kvmalloc with GFP_KERNEL | GFP_NOFAIL, followed by an OOM kill), code that assumed __GFP_NOFAIL would never return NULL could instead observe a NULL return and subsequently dereference it—causing kernel panics and system instability. The vulnerability was assigned in July 2024 and fixed upstream with a patch that refrains from checking fatal_signal_pending() when __GFP_NOFAIL is set, restoring the expected “never return NULL” behavior.
That fix has been backported and packaged by multiple Linux distributors (Ubuntu, SUSE, Oracle, Amazon Linux and others). Distribution advisories and vulnerability databases list the kernel fix and offer package-level remediation guidance for their affected kernel packages. The technical mitigation is simple in theory—apply kernel updates that include the upstream change—but the operational reality is that many environments run a variety of Microsoft-supplied and third-party images and artifacts that embed kernels in different ways, which complicates an “is it only Azure Linux?” binary question.

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What Microsoft actually published and what it means​

Microsoft’s Security Update Guide entries for a number of Linux kernel CVEs (the same FAQ language is used across several entries) state that Azure Linux includes this open‑source library and is therefore potentially affected, and that Microsoft began publishing machine‑readable CSAF/VEX attestations in October 2025; Microsoft also commits to updating CVE mappings if additional Microsoft products are identified as affected. That wording is a product-level attestation: it confirms Microsoft has completed the inventory for the Azure Linux product family and found the upstream component present. (msrc.microsoft.com)
Two points are important and commonly misunderstood:

• The attestation is an authoritative, machine‑readable signal for Azure Linux specifically — customers running Azure Linux should treat it as the canonical operational indicator. (msrc.microsoft.com)
• The attestation is not a universal guarantee that no other Microsoft product contains the same open‑source component. Microsoft explicitly says it will update the CVE entries if other products are found to ship the component. In other words, absence of a published attestation for another Microsoft product is not proof that the product is unaffected. (msrc.microsoft.com)

This distinction—authoritative attestation for the inventoried product versus an ongoing, phased inventory for the vendor’s full portfolio—is the single clearest operational takeaway from Microsoft’s wording and the heart of the user's question. Independent analyst write-ups and community discussion echo the same interpretation: take Microsoft’s affirmation about Azure Linux as definitive for that product, but assume uncertainty for other Microsoft artifacts until they are individually inventoried or patched.

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Why the “only Azure Linux?” interpretation is risky​

When a major vendor attests to a component being present in one product family, many administrators instinctively infer that the vendor checked everything and found no other carriers. That inference is attractive but risky for three practical reasons.

• Large vendors ship many kernel‑derived or Linux‑embedded artifacts: WSL kernels, custom cloud kernels (linux-azure variants), Marketplace VM images, management agents that bundle kernel modules, firmware bundles and appliances. Whether a given artifact contains the vulnerable code depends on the upstream kernel version, and on per-artifact kernel configuration (CONFIG_ flags), backport choices, and whether the relevant code was compiled in or removed. The Microsoft attestation covers the Azure Linux product family because Microsoft checked those artifacts*; it does not cover artifacts Microsoft has not yet fully inventoried.
• Kernel components are artifact‑level properties: two images built from the same distribution snapshot may differ if the build configuration or packaging trimmed drivers or compiled modules differently. Thus the mere presence of a vendor‑signed image does not automatically map to the same exposure across all vendor artifacts.
• Phased VEX/CSAF rollouts create a transient window of uncertainty: Microsoft and other vendors are increasingly publishing machine‑readable VEX attestations and SBOMs, but the rollout is incremental. During that period, there will be certified product families (like Azure Linux) and others that remain to be inventoried—so an attestation is a high‑fidelity yes for the product attested, not a universal no for everything else. (msrc.microsoft.com)

Operationally, this means that treating Microsoft’s attestation for Azure Linux as a signal to patch those images (and only those images) is necessary but not sufficient for enterprises that run a mixed footprint of Microsoft-supplied and third-party images.

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Practical examples of Microsoft artifacts that may still require verification​

To move from abstract to concrete, here are artifact classes Microsoft customers should verify in addition to Azure Linux images:

• WSL2 kernel images distributed for Windows clients. Microsoft publishes WSL kernel binaries and sources; whether a particular WSL build contains the vulnerable vmalloc path depends on the kernel version and config used to build that kernel. Treat WSL kernels as distinct artifacts that require inspection or confirmation via SBOM/VEX.
• linux‑azure kernels and kernel packages used to run Azure VM hosts or specialized services. Those kernels can be built with different configs or include backports; they’re not automatically identical to the Azure Linux distro images.
• Azure Marketplace VM images published by Microsoft or marketplace publishers; images often include kernel packages or prebuilt kernels that differ across publishers and versions, and those images may not be covered by the Azure Linux attestation unless specifically included in the inventory.
• Management or monitoring agents that ship kernel modules or kernel‑linked artifacts as part of their packaging; these are smaller risk classes but are often overlooked during inventory sweeps.
• Appliances and container base images that carry Linux kernels or kernel modules; some appliances include a minimal Linux environment that still contains kernel-level components compiled in.

Each of these artifact classes must be treated as potentially affected until verified.

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How to verify whether your Microsoft-supplied artifacts are exposed​

Customers should combine vendor-provided attestations with artifact-level scanning and SBOM inspection. Here’s a practical checklist you can apply immediately.

• Inventory all Microsoft-supplied artifacts you run (images, kernels, appliances, WSL kernels, Marketplace images). Start with what’s running in production and what’s in your CI/CD pipelines.
• For each artifact, obtain the SBOM or VEX/CSAF attestation from the publisher if available. Machine-readable files are now a standard source of truth for component presence. If Microsoft has published a VEX for the product family, use it as the canonical source for that family. (msrc.microsoft.com)
• If no SBOM/VEX is available, scan the artifact with an image scanner or perform package inspection (rpm -qa / dpkg -l / readelf on kernel images) to detect the vulnerable kernel version or backported patch. Many distribution advisories list the patched kernel versions you can use to verify.
• Prioritize patching: if an artifact is confirmed to contain the relevant kernel tree (or an affected backport), deploy the vendor-supplied kernel update or rebuild the image with updated packages. Distributors typically list the fixed versions and the release date; apply them according to your change window.
• For ephemeral or rapidly built images (CI runners, autoscaling nodes), bake patches into your image pipeline so every new instance launches with the fixed kernel. Use automated image scanning in CI to prevent regressions.

This approach blends Microsoft’s product attestation with artifact-level verification to produce a defensible, auditable remediation process.

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The technical fix and the real risk profile​

The upstream correction modifies vm_area_alloc_pages() to skip checking fatal_signal_pending() when GFP_NOFAIL is set—thereby ensuring that allocations flagged as “no-fail” will continue retrying instead of bailing out on fatal signals and returning NULL. In practice, the most likely real-world consequence of the bug is a local denial-of-service (kernel crash or panic) where code paths assumed non-NULL returns (for example, erofs kvmalloc users) dereference a NULL pointer. There is no widely documented remote exploitation chain for arbitrary code execution tied to this CVE; the chief impact is availability and stability.
Distribution and vendor advisories rate this vulnerability typically at medium severity (CVSS mid-range) because of the local attack vector and the availability-focused impact; but a kernel panic in a multi-tenant or high-availability environment can be operationally severe. The likelihood and impact depend on the presence of vulnerable code paths that use kvmalloc with GFP_NOFAIL and then assume that the allocation can never fail. Systems that perform aggressive memory operations under load or run filesystem drivers like erofs (which was the test case in the original report) are higher risk.

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Strengths and shortcomings of Microsoft’s current approach​

Strengths

• Product-scoped attestation is useful and precise. Microsoft’s explicit statement that Azure Linux includes the component gives Azure Linux customers an authoritative signal to prioritize remediation. That clarity is operationally valuable and reduces confusion for the product’s consumers. (msrc.microsoft.com)
• VEX/CSAF machine-readable attestations are the right direction. Publishing VEX/CSAF makes it easier for automation and governance tooling to consume verifiable product inventories and impact attestations, enabling faster, more deterministic patch prioritization where attested.

Shortcomings / risks

• Phased rollout produces temporary blind spots. Because the VEX/CSAF rollout is phased, there is a window during which only certain product families are inventoried. That creates a practical risk for organizations that run multiple Microsoft artifacts: the absence of an attestation for WSL or linux‑azure kernels is not evidence the artifact is safe.
• Assumptions about “Microsoft-supplied = safe” are dangerous. Customers often assume everything bearing Microsoft branding was comprehensively scanned; attestation practice shows that inventories happen product-by-product. Until Microsoft publishes attestations for other product families, customers must verify each artifact themselves.
• Operational communication could be clearer on artifact boundaries. The wording used by Microsoft is technically accurate but terse. Explicit examples in the MSRC entry (for example: “this attestation covers Azure Linux images and packages in the Azure Linux product family only”) would reduce misunderstanding among administrators. The community and industry write-ups have had to fill that gap.

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Recommended actions for WindowsForum readers and admins​

• Prioritize patching Azure Linux images and kernel packages if you run them: Microsoft’s attestation makes these the canonical first priority. Pull and deploy vendor-supplied kernel updates according to your change control calendar. Use distro advisories for precise package names and versions.
• Inventory and verify other Microsoft artifacts: treat WSL kernels, linux-azure kernels, Marketplace images, and any Microsoft-supplied appliances as separate artifacts. Obtain SBOMs or VEX attestations where available, and scan binaries/images where they are not.
• Automate image vetting in CI/CD: bake the fixed kernel packages into image builds and run automated image scans for CVE fingerprints before images enter production. For transient infrastructure, ensure new instances are launched from updated images only.
• Use compensating controls for hard-to-patch workloads: if you cannot immediately patch a class of images, reduce blast radius—limit network exposure, apply resource quotas (to reduce OOM pressure), and increase monitoring for kernel panics. Plan an accelerated patch window for these hosts.
• Subscribe to vendor attestation feeds and vendor advisories: Microsoft’s VEX/CSAF rollout is ongoing; subscribe to Microsoft’s security update feed and the distributor advisories relevant to your environment so you know when other product families are inventoried or when patches are published. (msrc.microsoft.com)

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When to treat Microsoft’s attestation as enough — and when to demand more​

Treat Microsoft’s Azure Linux attestation as sufficient when:

• You run only Azure Linux images and you have an asset inventory that maps your deployed hosts to that product family. In that case, the MSRC attestation lets you centrally prioritize and remediate. (msrc.microsoft.com)

Demand additional verification when:

• You run other Microsoft artifacts (WSL, linux-azure, Marketplace images, appliances) or third‑party images that might incorporate Microsoft-supplied kernel components. In that case, rely on SBOMs, image scanning and per-artifact verification. Microsoft’s wording explicitly allows for expansion of attestations; until that happens you must assume uncertainty.

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Conclusion​

The straightforward answer to the original question is: Microsoft’s public statement is authoritative for Azure Linux — it confirms that Azure Linux includes the open‑source component and should be considered potentially affected. However, it is not a proof that no other Microsoft product contains the same code. Microsoft’s attestation process is product‑scoped and phased; absence of a published attestation for other Microsoft artifacts is not evidence of absence. Operationally, the safest course for administrators is to treat Azure Linux attestation as a high‑confidence remediation priority and to complement it with artifact‑level verification (SBOM/VEX, image scanning, package inspection) across the rest of their Microsoft-supplied footprint. This dual approach—trust the attestation for what it covers, verify everything else—will close the practical blind spot that a single product-level statement inevitably leaves open. (msrc.microsoft.com)

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Source: MSRC Security Update Guide - Microsoft Security Response Center