Azure Linux CVE-2024-45002 Attestations and Cross Product Verification

Microsoft’s product statement on CVE-2024-45002 — that Azure Linux includes the implicated open‑source library and is therefore potentially affected — is accurate as a product-level attestation, but it is not the same thing as a global guarantee that no other Microsoft product contains the same upstream code. Customers should treat the Azure Linux attestation as authoritative for Azure Linux, and should perform artifact‑level verification for every other Microsoft‑supplied image, kernel, or distribution they run.

Background / Overview​

CVE‑2024‑45002 is a Linux kernel NULL pointer dereference in the rtla/osnoise component that can lead to a kernel crash (denial of service) when a specific error path mishandles a failed allocation. Upstream fixes were merged into the stable kernel branches and downstream Linux distributions released patches shortly afterward. Microsoft’s public security guidance for the CVE explicitly calls out Azure Linux as a product that includes the upstream component; the company also stated it has begun publishing machine‑readable CSAF/VEX attestations for vulnerabilities starting with Azure Linux and will update CVE/VEX records if additional Microsoft products are later found to ship the same component.
Those two sentences — a product attestation plus a process promise to expand attestations — are the root of the question many administrators are asking: Does the Microsoft statement mean Azure Linux is the only Microsoft product that could possibly be affected? The short, operational answer is: No — not necessarily. The long, practical answer that follows explains why, and then gives a concrete runbook you can use to verify exposure and remediate risk across environments that rely on Microsoft‑supplied artifacts.

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What Microsoft’s wording actually means​

Product attestation versus exclusivity​

When Microsoft says “Azure Linux includes the open‑source library and is therefore potentially affected,” it is making a product‑scoped inventory statement: Microsoft inspected the build artifacts for Azure Linux and found the upstream kernel component that corresponds to the CVE. That attestation is authoritative for Azure Linux customers and should be acted on.
That statement is not the same as asserting that no other Microsoft product includes the same upstream source. Practically speaking, Microsoft builds, publishes, or maintains a number of Linux artefacts and kernels across its product portfolio. Until those other artefacts have been inventoried and attested to via Microsoft’s CSAF/VEX or other disclosures, they remain unverified — not proven clean.

Why Microsoft started with Azure Linux​

Microsoft’s transparency rollout for CSAF/VEX began with Azure Linux as a pragmatic, phased approach. Azure Linux is a Microsoft‑curated distro used to produce the OS images consumed by many Azure services and customers. Starting with a single, cloud‑facing product simplifies coordination, validation, and automation for machine‑readable attestations. Microsoft has said it will extend this attestation process to more product families over time.
This is sensible from an operational standpoint, but it creates a window of uncertainty: until attestations for other Microsoft artefacts arrive, customers must assume they might be carrying the same upstream kernel code and verify for themselves.

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Why absence of an attestation is not proof of absence​

• Inventory gaps: Large vendors ship dozens of binaries, kernels, images and SDKs. A vulnerability that exists upstream can be present in any of these artefacts until explicitly inventoried.
• Kernel build variability: The presence or absence of a specific upstream change depends on the kernel version, patch set, and build configuration used to create a given kernel or image. Two kernels labelled “linux” can differ significantly.
• Multiple supply channels: Microsoft distributes Linux artifacts via different channels — cloud images, marketplace images, appliance bundles, container images, and the WSL2 kernel — each of which needs its own verification.
• Timing: Attestations are published as inventories are completed. A missing attestation may simply mean the product hasn’t been inventoried yet.

In short: treat an attestation as positive evidence (this product includes the component), and the lack of an attestation as no evidence either way.

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Who could also be affected (examples)​

Any Microsoft product or service that ships or supplies a Linux kernel build, kernel module, or image could theoretically include the rtla/osnoise component until validated. Examples that require explicit checking include:

• Windows Subsystem for Linux (WSL / WSL2) — Microsoft supplies a Linux kernel binary for WSL2; the kernel build used determines which upstream fixes are present.
• linux‑azure kernels used for some Azure virtual machine families — these are Microsoft‑packaged kernels and can differ from Azure Linux images.
• Azure Marketplace images and curated VM images that include Microsoft‑provided kernels or kernel modules.
• AKS node images or managed node pools that rely on Microsoft‑curated distributions.
• Appliances and published images (for example, Marketplace or partner images Microsoft distributes).
• Any Microsoft SDKs, tools or containers that embed Linux kernel code (less common, but worth inventorying).

This list is illustrative, not exhaustive. The only way to be sure for your environment is to perform artifact‑level inspections.

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Technical summary of the vulnerability (brief)​

• Root cause: In the rtla/osnoise kernel code, an error path calls osnoise_free_top() when tool->data allocation fails; calling that on NULL can produce a NULL pointer dereference.
• Impact: Local attacker or process with the ability to trigger the code path can cause a kernel crash (availability impact). There is no direct evidence this allows code execution or data disclosure; the primary effect is denial of service.
• Fixed upstream: Kernel stable branches received fixes in releases that close the affected ranges; downstream distributions issued security updates that incorporate the upstream fix.
• Affected ranges: Affected kernel versions fall into several branch ranges; vendors listed fixed stable versions as the remediation points. (Operators should compare the kernel builds in their fleet against the affected ranges supplied by upstream/distributions.)

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How to verify whether your Microsoft‑supplied artifact includes the vulnerable code​

You need to run a short and precise verification workflow for each distinct Microsoft image or binary you run. Below is a practical runbook you can use immediately.

Quick checklist (high level)​

• Identify every Microsoft‑supplied kernel/image/VM you run.
• For each artifact, identify the kernel version and build metadata.
• Inspect the kernel configuration and the kernel binary for the presence of the rtla/osnoise component.
• If the artifact is affected, apply the vendor or upstream patch or replace the image with a patched build.
• Monitor vendor VEX/CSAF attestations for updates from Microsoft.

Concrete steps to inspect an individual Linux host or image​

• Determine the running kernel and the vendor package:
• Run: uname -a (or check image metadata).
• Check package manager: dpkg -l linux-image or rpm -qa 'kernel' where applicable.
• Compare the kernel version to the affected ranges:
• If your kernel version falls within the upstream affected ranges, proceed to the next checks.
• If your kernel is newer than the patched upstream stable releases (or is a vendor package that claims a security patch), you may already be fixed — but verify the vendor advisory or package changelog.
• Check for kernel config and module traces:
• If /boot/config-$(uname -r) or /proc/config.gz is available, search for symbols related to the component by name (for example, search for strings like “osnoise” or “rtla” in the config or build-time options).
• Use strings or readelf on the vmlinuz or kernel image to search for embedded symbol names when config is missing. For example: strings /boot/vmlinuz-$(uname -r) | grep -i osnoise
• Search installed modules and kernel symbols:
• Check /lib/modules/$(uname -r) recursively for files referencing “osnoise” or similar strings.
• Use: cat /proc/kallsyms | grep osnoise (requires privileged access).
• If inspecting an image file (offline), mount or extract the image and perform the same file and string searches on the kernel binary and module directory.
• For Microsoft containers, SDKs, or published binaries distributed by Microsoft, rely on the vendor SBOMs (if available) and VEX/CSAF attestations, and perform binary inspection where SBOMs are absent.

Note: Kernel symbols and names can be obfuscated or stripped in some builds; absence of textual matches is informative but not conclusive. When in doubt, contact the vendor or rebuild the image with a known patched kernel.

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Patching and mitigation guidance​

What to patch​

• Azure Linux customers: Follow Microsoft’s announced update stream for Azure Linux images and kernels. If Microsoft has published a patched kernel image for Azure Linux, prioritize applying that update to affected Azure VM instances and images.
• Other Microsoft images and artifacts: If you find the vulnerable component in a Microsoft‑supplied image, follow the product’s update guidance — apply the new image, kernel package, or patch. If no guidance exists yet, isolate and escalate to Microsoft support and treat the artifact as vulnerable until patched.

Upstream and distribution fixes (operationally useful)​

• The upstream kernel maintainers merged fixes into the stable branch lines; downstream distributions (Ubuntu, Debian, SUSE, and others) subsequently produced security packages that include the fix.
• Where a vendor package is available with the fix, install the vendor-supplied update rather than attempting to backport the single patch, unless you maintain custom kernels and are comfortable building and validating kernel images.

Short-term mitigations if patching is delayed​

• Limit local process access — because exploitation requires local invocation of the code path, reduce the set of users and processes that can interact with the subsystem or run untrusted code.
• Harden access controls — enforce strict user quotas and access controls on multi-tenant hosts.
• Monitor for crashes — increase monitoring and alerting for kernel oopses and reboots. If crashes occur in tandem with workloads that might trigger the code path, treat them as higher priority.
• Use image replacement — if a Microsoft image is unpatched and you cannot wait for the vendor response, replace it with an alternative image that has a patched kernel from your preferred distribution, or rebase workloads to patched nodes.

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Operational priorities and recommended runbook​

Follow this ordered, prioritized process across your organization.

• Inventory:
• Build a list of every Microsoft‑supplied kernel, image, or VM image you run (Azure images, WSL kernels, Marketplace appliances, AKS node images, etc.).
• Triage:
• For each item, determine whether Microsoft has published a VEX/CSAF attestation confirming inclusion (positive) or a “not affected” or “under investigation” status. Treat attestations as authoritative for that artifact.
• Verify:
• For any un‑attested Microsoft artifact in your inventory, perform the artifact‑level inspection steps above (kernel version, symbol search, module checks).
• Patch or replace:
• Apply vendor or upstream fixes to affected artifacts. For Azure Linux, follow Microsoft’s image updates. For other images, apply distribution packages or replace with patched images.
• Mitigate:
• If immediate patching is impossible, apply short‑term mitigations (restrict local access, monitor for crashes, reimage high‑risk hosts).
• Track:
• Subscribe to Microsoft’s CSAF/VEX feeds and your distribution vendor advisories for updates. Microsoft has committed to updating its CVE records if additional Microsoft products are identified as carriers — monitor those updates.

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Practical examples: how this looks in the wild​

• If you run Azure Linux images, Microsoft has already attested that the component exists there; apply Azure Linux security updates without delay.
• If you run WSL2 on Windows clients, check the WSL kernel version shipped to your devices. Because Microsoft provides the WSL kernel binary, you must verify whether it contains the vulnerable code or whether a patched WSL kernel has already been published. Don’t assume desktop clients are unaffected without checking the kernel version.
• If you maintain a fleet of AKS node images or use curated Marketplace appliances, add those image identifiers to your inventory list and run the artifact checks described earlier.

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Risks, strengths, and why Microsoft’s approach is defensible — plus warning flags​

Notable strengths in Microsoft’s approach​

• Transparency move: Publishing CSAF and VEX attestations is an important advance for supply‑chain clarity. Machine‑readable attestations enable automated tooling and faster triage.
• Practical phased rollout: Starting with Azure Linux allows Microsoft to validate processes before scaling to many diverse products. That reduces the chance of incorrect attestations.
• Clear promise to update: Microsoft committed to update CVE/VEX records if additional products are identified — that’s a helpful operational signal for customers.

Potential risks and limitations​

• Time window of uncertainty: Until VEX inventory coverage expands, customers who rely on other Microsoft images may be left to perform manual verification. This is an operational burden for security teams that manage diverse cloud and hybrid environments.
• Perception of exclusivity: Short public statements that single out one product without clearly explaining that more attestation is forthcoming can be misread as a claim of exclusivity. This drives confusion and inconsistent risk prioritization.
• Artifact‑level complexity: Kernel differences between products make blanket assertions difficult; customers must be diligent with per‑artifact checks, which is time consuming.

How customers should read vendor language​

When a vendor attests that “Product X includes component Y and is potentially affected,” treat that as a documented finding for that product. When the vendor follows with “we will update this CVE if additional products are identified,” treat that as a process commitment, not a statement that no other products could contain the component. Always validate the vendor attestations against your environment.

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If you find the vulnerable component in a Microsoft product: how to escalate​

• Document the artifact identifier (image name, build id, kernel version).
• Check whether Microsoft has published an attestation or published fix for the artifact.
• If no fix or attestation exists, contact Microsoft support with your artifact details and request clarification or a remediation timeline.
• In parallel, treat the artifact as vulnerable and apply compensating controls (isolate, replace image, or restrict access) until patched.

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Summary and final advice​

Microsoft’s public statement that Azure Linux includes the rtla/osnoise component implicated in CVE‑2024‑45002 is an authoritative product attestation for Azure Linux customers, and those customers should prioritize the vendor’s Azure Linux patches. However, that attestation does not equate to a guarantee that no other Microsoft product contains the same upstream code. Microsoft’s CSAF/VEX rollout began with Azure Linux and will expand; until it does, absence of an attestation is not evidence of absence.
Operationally, security teams should:

• Treat the Azure Linux attestation as high priority and patch Azure Linux images promptly.
• Inventory every Microsoft‑supplied kernel or image in their environment and perform artifact‑level checks.
• Compare kernel versions to the upstream affected ranges and inspect kernel binaries and modules for osnoise/rtla traces where determinable.
• Apply vendor or upstream patches, replace images with known‑good builds, and apply compensating controls where immediate patching is not possible.
• Monitor Microsoft’s CSAF/VEX feeds and vendor advisories for updates and newly published attestations.

The practical reality of modern supply chains is that a single upstream change can manifest across multiple vendor artifacts. The safest operational posture is to assume shared exposure until you can demonstrate otherwise through inventory, inspection, and vendor attestations.

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Source: MSRC Security Update Guide - Microsoft Security Response Center