CVE-2024-43914: Azure Linux Attestations and Microsoft Artifact Scope

Microsoft’s short, product‑scoped statement that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate but not exclusive — it affirms that Azure Linux images have been inventory‑checked and found to contain the vulnerable md/raid5 code, but it does not prove that no other Microsoft product or image can contain the same upstream file or be in scope for CVE‑2024‑43914.

Background / Overview​

CVE‑2024‑43914 is a medium‑severity Linux kernel defect in the MD (software RAID) code — specifically the md/raid5 path — that could trigger a kernel BUG_ON() during a particular reshape/revert sequence, producing a kernel panic and a local‑vector denial of service. The vulnerability was publicly tracked in 2024 and subsequently patched in upstream stable trees; vendors and distributions have pushed fixes into their kernel packages and backports. Public trackers (for example AWS’s CVE tracking and SUSE’s advisory) list the CVSSv3 base score as 5.5 and enumerate affected kernel series and vendor remediation dates.
Microsoft’s MSRC advisory for this (and similar Linux kernel CVEs) follows a pattern: the update guide will state that Azure Linux includes the implicated open‑source component and is therefore potentially affected, and Microsoft has committed to publishing machine‑readable VEX/CSAF attestations — starting with Azure Linux and expanding to other products on a phased basis. That rollout (announced October 22, 2025) is intended to clarify which Microsoft artifacts are Known Affected, Not Affected, Under Investigation, or Fixed for a given CVErms, the MSRC line is an attestation of inspection for Azure Linux, not an exhaustive corporate statement that every Microsoft shipping artifact has been scanned and cleared.

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What Microsoft’s wording means — and what it doesn’t​

The precise meaning (what MSRC is actually saying)​

• Microsoft has inventory‑checked the Azure Linux distribution (the images and kernel packages Microsoft builds and publishes under that product family) and found the upstream md/raid5 code that maps to CVE‑2024‑43914. Azure Linux is therefore in‑scope for remediation, and Microsoft will include it in VEX/CSAF attestations.
• Microsoft will update the CVE page and its VEX attestations if additional Microsoft products are subsequently found to ship the same vulnerable code. This is an explicit commitment rather than an implicit guarantee of completeness. (microsoft.com)

The common misinterpretation to avoid​

• Do not read Microsoft’s Azure‑focused language as a categorical exclusive statement that no other Microsoft product includes the vulnerable md/raid5 code. Microsoft ships hundreds of Linux kernel artifacts — WSL2 kernels, Azure Marketplace images, AKS node images, appliance images, and custom kernels in platform services — and whether any specific artifact is affected depends on the kernel version range and kernel config used when the artifact was built. The presence of identical upstream files in multiple artifacts is entirely plausible; the attestation only confirms what Microsoft has completed so far.

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Which Microsoft artifacts could plausibly carry the vulnerable md/raid5 code?​

Technically, any Microsoft‑distributed artifact that contains a Linux kernel built from an affected upstream range and that enables the MD subsystem (CONFIG_MD or CONFIG_BLK_DEV_MD) could include the vulnerable md/raid5 path. Notable examples to check in your estate:

• Azure Linux distribution images — Microsoft has already attested these as potentially affected and is publishing VEX/CSAF status for them.
• WSL2 kernel builds — Microsoft maintains and publishes the WSL2 kernel source and configurations in a public Git repository; WSL’s kernel builds are derived from upstream trees and can enable or disable subsystems per the WSL config. Whether a particular WSL2 kernel is vulnerable depends on the exact kernel commit and the configured options like CONFIG_MD. You cannot assume WSL2 is unaffected purely because it runs on Windows — check the kernel build and config.
• Azure Marketplace images, AKS node images, and other VM images — Microsoft and third‑party publishers ship many kernel artifacts; some include distribution kernels or Microsoft‑tuned kernels which may carry MD support. Inventory these images via their SBOMs or package metadata.
• Appliances and container host images — OEM or partner images published on Microsoft marketplaces might include kernels with MD enabled.
• Specialized platform kernels used by services (some Azure platform agents) — these are less likely to expose MD functionality to tenants but still require artifact‑level verification.

Said simply: Azure Linux was explicitly checked and attested by Microsoft; other Microsoft artifacts may contain the vulnerable upstream file depending on what kernel source and config were used when the artifact was built. This is both a practical reality and the reason Microsoft is rolling out VEX/CSAF attestations incrementally.

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How to determine whether a Microsoft artifact you run is affected — practical checklist​

The only reliable way to determine exposure is artifact‑level verification. Below is an operational triage playbook you can follow immediately.

• Identify the kernel artifact
• For running Linux hosts: run uname -r to get the kernel rel WSL2: check the WSL kernel version string inside the distribution or consult the WSL2 repo/config used at build time.
• For Azure VM/Marketplace images: retrieve the image manifest, SBOM, or kernel package metadata.
• Map kernel versions to the CVE
• Use vendor advisories, NVD/OSV entries, or trustworthy trackers (SUSE, Amazon Linux ALAS, Red Hat) to find fixed kernel versions or the commit ranges that contain the fix. For CVE‑2024‑43914, multiple vendor trackers list the affected series and the CVSSv3 base score 5.5.
• Check whether the MD subsystem is enabled
• On a running host: Inspect kernel config at /proc/config.gz (zgrep CONFIG_MD /proc/config.gz) or check the compiled config file shipped by the distro. Look for CONFIG_MD and CONFIG_BLK_DEV_MD (built‑in = y or module = m). If MD isn’t enabled, the md/raid5 code cannot be triggered. If MD is modular, check lsmod | grep md to see whether modules are loaded.
• If you manage images rather than running hosts
• Inspect the image SBOM or package manifest for the kernel package and kernel config. If an image is Microsoft‑supplied, consult Microsoft’s CSAF/VEX entries (when available) for that product — Azure Linux is VEX‑attested early in the rollout.
• If uncertainty remains, assume in‑scope and patch
• Where you cannot confirm absence, treat the artifact as potentially affected until you verify. The operational cost of patching and rebooting kernels is usually lower than the risk of unplanned panics in production systems.

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Technical verification: what to look for in kernel and vendor data​

• Upstream fix commit(s): the md/raid5 change is small and defensive (remove BUG_ON / adjust checks to WARN and handle error paths). Confirm whether your kernel’s commit history or vendor package changelog includes the upstream patch. Vendor advisory entries often list the commit or stable patch ID.
• Vendor package fixes and patch dates: for example, some vendors published fixed packages in early 2025 (Amazon Linux listed vendor fixes in March 2025). Cross‑reference your distro’s errata and package versions to ensure you pick a fixed kernel package.
• Kernel config flags: verify CONFIG_MD / CONFIG_BLK_DEV_MD and whether md is built‑in. A kernel with MD disabled is not vulnerable in practice for this particular path. Use /proc/config.gz or the distro’s config file to check.

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Risk analysis: who should be most concerne software RAID (mdadm) or environments that rely on MD in their kernels are the primary at‑risk group: the vulnerable code is in the md/raid5 path and is exercised by reshape/revert sequences. Systems that do not enable MD are not practically affected.​

• Cloud images and virtual appliances that rely on distributed or early boot reshape semantics should be triaged carefully. Unexpected kernel panics during reshape/reassembly can be disruptive for cluster nodes, CI runners, or diskless boot scenarios.
• Multi‑tenant build hosts, CI runners, or any environment where untrusted users could trigger mdadm operations are particularly sensitive from an operational standpoint. Local, unprivileged triggers can be enough to exercise the problem sequence.

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Immediate mitigations and remediation recommendations​

• Apply vendor/kernel patches: the only full fix is installing the patched kernel release or the vendor backport for your distribution and rebooting into it. Vendor advisories (NVD, distribution security pages) list fixed package names and versions.
• If you cannot patch immediately:
• Disable MD support in environments that do not need software RAID: blacklist md modules or boot a kernel compiled without CONFIG_MD. This reduces the attack surface but may be impractical where software RAID is required.
• Limit who can run mdadm or manage devices that could trigger reshape operations: tighten sudo policies and container isolation on build hosts or shared systems.
• For WSL2 users:
• Verify the WSL2 kernel build and config. Where WSL shipped kernels use a Microsoft kernel build, confirm the kernel version and configuration and adate or WSL‑supplied kernel update as advised. Custom WSL kernels can be rebuilt with a fixed upstream.
• Maintain SBOM and artifact inventories:
• Use SBOMs, package metadata, image manifests and Microsoft’s CSAF/VEX attestations (as they roll out) to automate identification of affected artifacts. Microsoft’s VEX rollout began with Azure Linux and will expand; leverage it when available, but do not wait on it exclusively.

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Why Microsoft’s phased VEX rollout matters — and its current limitations​

Microsoft’s decision to publish machine‑readable VEX/CSAF attestations starting with Azure Linux is a meaningful step: it supplies customers with programmatic attestation about exploitability and impact status for that product family, reducing guesswork. However, the rollout is intentionally phased — starting with one product — so customers cannot assume CISA‑style completeness across Microsoft’s entire ecosystem yet. Until attestations are published for each product, customers must rely on artifact‑level scanning and vendor advisories to identify exposure.
The practical upshot:

• If you run Azure Linux images: treat Microsoft’s attestation as authoritative and apply Microsoft’s updates per their guidance.
• If you run other Microsoft‑supplied artifacts (WSL2, Marketplace images, AKS nodes, appliansume safety. Verify kernel versions and configs, consult VEX/CSAF when available, and patch or mitigate as required.

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A short technical note for sysadmins and kernel teams​

• Commands to run on a host for triage (example checklist):
• uname -r — get the kernel version string.
• zgrep CONFIG_MD /proc/config.gz || grep CONFIG_BLK_DEV_MD /boot/config-$(uname -r) — determine whether MD is enabled.
• lsmod | grep md — see whether MD modules are present.log kernel | sed -n '1,80p' or apt changelog for kernel packages — check vendor changelogs for the CVE mapping.
• Inspect image SBOM or manifest for Microsoft images if you mahen triaging WSL2 kernels, recall that Microsoft publishes the WSL2 kernel source and config routinely. The kernel config used by the WSL team determines which subsystems are enabled; you can rebuild a custom kernel with MD disabled if necessary.

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Strengths and limitations of the upstream and vendor response​

Strengths

• The upstream fix is small, targeted, and merged into multiple stable kernel trees; that makes it straightforward for downstream maintainers and vendors to backport and release patches. Public reproducer reports and vendor advisories accelerated distribution updates.
• Microsoft’s VEX/CSAF initiative improves transparency for customers once extended across more products. The October 2025 blog explains the phased rollout and the expected benefits of machine‑readable attestations.

Limitations / residual risks

• The real risk window is deployment lag: many images, appliances, and embedded kernels are slow to update. Earth‑moving changes like kernel package upgrades and reboots take time in production fleets.
• Microsoft’s current Azure‑first attestation model provides immediate clarity for Azure Linux, but other Microsoft artifacts remain un‑attested until inventory work is complete; this leaves a verification burden on operators that run diverse Microsoft images.

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Practical recommendations (priority checklist)​

• If you run Azure Linux: follow Microsoft’s remediation guidance first and apply the published kernel updates. Azure Linux is a confirmed carrier in Microsoft’s current attestation set.
• Inventory all Microsoft artifacts you run (WSL kernels, Marketplace/AKS images, appliances) and map their kernel versions against the CVE affected ranges. Use SBOMs and image metadata where available.
• Check CONFIG_MD / CONFIG_BLK_DEV_MD in the kernel configs for those artifacts. If MD is absent, the md/raid5 path cannot be triggered. If MD is present, prioritize patching.
• Apply vendor patches and schedule reboots as required. Where immediate patching isn’t possible, consider blacklisting MD modules in non‑RAID hosts and tightening access to mdadm and sysfs interfaces.
• Automate detection: add kernel version mapping and CONFIG_MD checks to your vulnerability scanning and SBOM ingestion pipelines so you can triage future Linux kernel CVEs faster.

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Conclusion​

Short answer to the user’s question: No — Azure Linux is not necessarily the only Microsoft product that could include the vulnerable md/raid5 code; it is simply the product Microsoft has explicitly attested as potentially affected so far. That attestation is valuable and authoritative for Azure Linux customers, but it is product‑scoped, not exhaustive across all Microsoft artifacts. Until Microsoft’s VEX/CSAF attestations cover additional products, operators should perform artifact‑level verification — checking kernel versions, kernel configs (CONFIG_MD), SBOMs, and vendor advisories — to determine exposure and to prioritize patching.
If you want, I can draft a short script or a checklist you can run across a fleet (hosts, WSL instances, and images) to automatically flag artifacts that match the vulnerable kernel ranges and have MD enabled.

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Source: MSRC Security Update Guide - Microsoft Security Response Center