CVE-2024-44946: Azure Linux Attestation and How to Verify Microsoft Artifacts

The short answer is: Microsoft has publicly attested that Azure Linux includes the upstream Linux kernel component implicated by CVE‑2024‑44946, but that attestation is a product‑level statement — it is not a technical guarantee that no other Microsoft product or image can contain the same vulnerable kernel code. In plain operational terms: treat Azure Linux as a confirmed, high‑priority remediation target; treat other Microsoft artifacts (WSL kernels, Marketplace images, AKS/VM kernels, custom kernel builds shipped by Microsoft, and container images) as unverified until you or Microsoft confirm them — do not assume they are automatically safe.

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Background / Overview​

CVE‑2024‑44946 is a Linux kernel concurrency defect in the Kernel Connection Multiplexor (KCM) socket implementation that allowed a race between two threads building and queuing the same socket buffer (skb). The race could lead to a double‑free / use‑after‑free in kcm_release(), producing memory corruption and potential kernel crashes or instability. The upstream fix serialises kcm_sendmsg() for the same socket by taking a per‑socket lock so concurrent sendmsg() callers cannot corrupt the shared skb state.
Multiple distro and vendor trackers recorded the issue, assigned a medium severity score (CVSS ≈ 5.5), and published the same technical description and remediation guidance. Major Linux distributions and cloud images (for example Amazon Linux, Debian/Ubuntu, Oracle Linux, Red Hat‑tracked updates) repackaged the kernel fixes into kernel updates or backports. That broad distro-level coverage shows this is an upstream kernel issue, not a vendor‑unique component.
Why that matters: a kernel bug like this is an artifact‑level risk. Whether a given product or binary is vulnerable depends on what kernel commit set and configuration were compiled into the shipped kernel image, and whether that image includes the KCM code paths. You cannot determine vulnerability solely from a product name unless you have either vendor attestations or you have inspected the binary artifacts yourself.

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What Microsoft has said — and what it actually means​

Microsoft’s Security Response Center (MSRC) entry for CVE‑2024‑44946 includes the now‑familiar FAQ phrasing that has appeared on many Microsoft CVE pages: “Azure Linux includes this open‑source library and is therefore potentially affected by this vulnerability.” The statement also notes Microsoft’s commitment to publish machine‑readable CSAF/VEX attestations (the VEX rollout began in October 2025) and to update the CVE mapping if other Microsoft products are discovered to carry the implicated code.
Two points to parse from that wording:

• Authoritative product attestation for Azure Linux. Microsoft inspected the Azure Linux build artifacts and found the upstream kernel code that maps to CVE‑2024‑44946. That makes Azure Linux a known carrier and therefore a clear remediation priority for customers who run Azure Linux images. Treat the MSRC attestation as a high‑confidence signal for that product.
• Not an exclusivity guarantee. That same short sentence is not a proof that every other Microsoft product is free of the vulnerability. Microsoft’s VEX/CSAF rollout is phased and product‑by‑product; absence of an attestation for a different Microsoft product is absence of attestation, not proof of absence. In practice, Microsoft publishes attestations for the Azure Linux family first and will expand coverage; it explicitly states it will update CVE records if it finds additional Microsoft products that ship the same code. Do not conflate “attested” with “only.”

This distinction is central to secure operations: a vendor attestation is a slice of inventory work, not a forensic scan of every binary image that vendor has ever produced.

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Why other Microsoft artifacts could be carriers​

There are multiple plausible paths by which the same upstream kernel code (and therefore the same vulnerability) might appear inside other Microsoft artifacts:

• Microsoft publishes and maintains a separate Linux kernel tree for Windows Subsystem for Linux (WSL2), with official kernel releases and configurations. Those kernel builds are built from upstream trees and from Microsoft’s kernel branches; if a WSL kernel release contains a kernel commit set that either lacks the CVE fix or backport, the problem could appear there. Microsoft’s WSL kernel repo and release tags are publicly available, and Microsoft updates those kernel releases over time.
• Microsoft builds and publishes multiple kernel images used across Azure: Azure VM images, Marketplace images, Azure‑tuned kernel packages (for example linux‑azure or custom VM kernel builds), AKS node images, and other images used by platform services. Whether those images include the vulnerable commit depends on the exact kernel version and build configuration in each image; Microsoft’s Azure Linux attestation covers the Azure Linux distribution image set, but it does not automatically cover all other Azure images or marketplace appliances.
• Microsoft’s developer tooling, package managers, and published container base images can carry copies of upstream code or ship kernels as part of images customers download. That can create second‑order carriers even if a particular product owner is not shipping a kernel directly.

Because of these different distribution vectors, the correct defensive posture is to verify the kernel artifact you run (or that Microsoft supplies to you) rather than relying on a single product statement.

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How to verify whether a specific Microsoft artifact is affected​

If you manage systems that run Microsoft‑supplied artifacts (Azure VMs, AKS nodes, Marketplace images, WSL2 instances, or Microsoft container images), follow the steps below to move from “unknown” to “known” status.

1. Identify the kernel binary and version​

• On Linux systems, run:
• uname -a
• uname -r
• On WSL2, check the WSL kernel version reported by the Linux guest with uname as above; Microsoft publishes WSL kernel release tags in the WSL kernel repo so you can map a version to commit history.

2. Check the kernel config and module files for KCM​

• Check whether the kernel was built with KCM code or whether a KCM module is present:
• zgrep -i kcm /boot/config-$(uname -r) || grep -i kcm /proc/config.gz (if /proc/config.gz is available)
• grep -R "net/kcm" /lib/modules/$(uname -r) || find /lib/modules/$(uname -r) -type f -exec nm -A {} \; 2>/dev/null | grep -E "kcmsock|kcm_sendmsg"
• If the kernel config is not present on the image, inspect the package manifest or binary module list for net/kcm or the kcm implementation files. (Note: not every kernel uses a CONFIG_KCM symbol; presence is best verified by searching for the KCM symbol names or net/kcm module artifacts in the modules tree.)

If you find that your kernel includes the KCM code and the kernel version predates the upstream fix or the vendor backport, treat the system as affected and remediate. If you cannot determine from the image, escalate to vendor support for a VEX/CSAF attestation or SBOM.

3. Cross‑check vendor advisories and fixed kernel versions​

• Compare your kernel version to the upstream kernel commit that introduced the fix and to the distribution vendor advisories (Debian/Ubuntu, Red Hat, Amazon Linux) which list fixed package versions. NVD, OSV and vendor trackers record the CVE and fixed kernel ranges — use them to map package names and kernel releases you must update to.

4. For WSL: check which kernel your Windows host is running and whether Microsoft has published an updated kernel release that contains the fix​

• Microsoft publishes the WSL kernel tree and release tags; if you run the default WSL kernel provided by the system, check whether Microsoft’s WSL releases include the upstream fix for the commit that resolved CVE‑2024‑44946. If you run a custom WSL kernel, rebuild using a patched upstream tree.

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Remediation and mitigation guidance​

• Azure Linux customers — apply Microsoft updates first. The MSRC attestation makes Azure Linux a known carrier; patch Azure Linux images and kernels according to Microsoft’s published updates as the top priority. Microsoft has mapped the component to Azure Linux and will provide the kernel updates or packages for those images.
• Update any Microsoft‑supplied kernel artifacts you run (WSL, Azure kernels, Marketplace images, AKS nodes). If an image or kernel is under your control (for example a Marketplace image you deployed), check the kernel version and apply vendor kernel updates or replace the image with a patched image. If the artifact is managed by Microsoft but not in the Azure Linux family (for example, a WSL default kernel or a Marketplace image), check Microsoft’s VEX/CSAF outputs or ask Microsoft support for explicit attestation.
• Rebuild or replace custom kernels and images. If you build custom WSL kernels or custom VM kernels for cloud appliances, rebuild them from an upstream tree that includes the kcm fix or apply the backport to your build branch.
• Apply defensive hardening as a stop‑gap. Because this is a local concurrency bug, the immediate exploitability requires local access and carefully timed race conditions; if you cannot immediately patch every artifact, reduce local attack surface (restrict local user accounts, container isolation, and unprivileged user access), and accelerate kernel patching in environments that accept untrusted local workloads.
• Subscribe to MSRC VEX/CSAF updates and vendor advisories. Microsoft explicitly said it would update the CVE mapping if additional Microsoft products are identified as carriers; subscribe to MSRC feeds and your distribution vendor advisories to receive notice when additional artifacts are attested as affected or fixed.

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Practical checklist for administrators​

• Inventory: list all Microsoft‑provided images you run (Azure VM SKUs, Marketplace images, AKS node images, WSL2 instances, Microsoft container images).
• Probe: for each image, query uname -r and inspect /boot/config* or module lists for KCM code or net/kcm artifacts.
• Cross‑reference: map each kernel version to vendor/distro CVE advisories and upgrade to fixed kernel packages where available.
• Patch: prioritize Azure Linux images then expand to other Microsoft kernels you actually run.
• Ask: where MSRC VEX/CSAF does not cover an artifact you run, ask Microsoft support for an explicit attestation or SBOM for that artifact.

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Risks of misreading the Microsoft attestation​

• Under‑patching other images: Interpreting “Azure Linux includes the library” as “only Azure Linux includes it” risks leaving other Microsoft‑maintained kernels or images unpatched. That can leave your estate exposed if any of those images included the upstream commit set pre‑fix.
• Over‑reliance on single signal: Conversely, treating any absence of attestation as “safe” will also cause blind spots. The safe operational stance is to treat un‑attested artifacts as unknown and verify them.
• Automation blindspots: Automated scanners that only consult MSRC VEX for “affected” status may miss Microsoft artifacts that haven’t been attested yet. Combine vendor attestations with artifact scanning and kernel config checks.

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Why Microsoft’s phased VEX approach is sensible — and its limits​

Microsoft’s approach (start with Azure Linux, publish CSAF/VEX attestations, then expand) is a practical, phased rollout of supply‑chain transparency. Producing per‑product attestations and SBOM‑style mappings for thousands of artifacts is laborious, so starting with a single Microsoft‑managed distro is a sane initial step. Microsoft has published a blog post describing the October 2025 VEX rollout for Azure Linux and their intention to expand attestations.
Limitations are operational: while VEX/CSAF gives customers a machine‑readable way to prioritize patching for attested products, it cannot instantly prove that every other Microsoft binary image is clean. That verification still requires either vendor attestations for each artifact or independent artifact inspection by the customer. The MSRC advisory language makes this point explicit: Microsoft will update CVE/VEX records if additional products are discovered to be carriers.

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Conclusion — recommended action summary​

• If you run Azure Linux images: update immediately following Microsoft’s kernel update guidance. Azure Linux is a confirmed carrier per MSRC; treat it as the top priority.
• Inventory Microsoft‑supplied artifacts across your estate (WSL kernels, Marketplace images, AKS nodes, VM images) and verify kernel versions and module lists for the KCM code paths. If you find the KCM code in a kernel pre‑fix, plan an immediate update or image replacement.
• Don’t assume that absence of a Microsoft VEX/CSAF attestation equals safety. Absence of attestation is not proof of absence; treat un‑attested artifacts as unknown until verified.
• Subscribe to MSRC and distro vendor advisories, and request VEX/CSAF attestations for any Microsoft artifact you rely on but is not yet covered by Microsoft’s published attestations.
• Use the practical verification steps above (uname, kernel config checks, module searches) to determine whether a given image is affected, and patch or replace accordingly.

Bottom line: Microsoft has done the right thing by publicly attesting Azure Linux and by committing to VEX/CSAF transparency. That attestation gives Azure Linux customers a precise, actionable signal. But defenders must not stop there — inventory and artifact‑level verification remain essential because other Microsoft artifacts may, depending on kernel versions and build choices, include the same vulnerable KCM code.

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Source: MSRC Security Update Guide - Microsoft Security Response Center