CVE-2024-42074: Azure Linux Attestation and Kernel Safety

Microsoft’s short MSRC advisory that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate — but it is an inventory attestation, not a technical guarantee that no other Microsoft product could contain the same vulnerable Linux kernel code. erview
CVE-2024-42074 is a Linux kernel robustness bug fixed upstream by a small defensive change: a null check added for the chip_pdev pointer in the AMD ASoC (audio subsystem) code path — specifically inside snd_acp_resume() — to avoid a NULL‑pointer dereference when an ACP platform device is skipped during probe. This change was incorporated into the kernel stable trees and is tracked in public vulnerability databases.
Microsoft’s public CVE entry for this issue names Azure Linux (the Microsoft-maintained CBL‑Mariner/Azure Linux product family) as a product that “includes this open‑source library and is therefore potentially affected,” and also states Microsoft began publishing machine‑readable CSAF/VEX attestations in October 2025 and will update CVE mappings if additional Microsoft products are found to ship the same code. That wording has prompted a common question: does that mean Azure Linux is the only Microsoft product that could be affected? The short answer for operations teams is: no — not necessarily. Microsoft has attested Azure Linux because that product was inventoried; absence of attestations for other Microsoft artifacts is not proof those artifacts are clean.
This article explains the technical fix, clarifies what Microsoft’s attestation means in practice, analyzes the residual risks for enterprise operators, and provides step‑by‑step verification and mitigation guidance you can apply to Microsoft-supplied artifacts and your estate.

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What CVE-2024-42074 actually is​

Technical summary​

• Vulnerability ID: CVE-2024-42074.
• Component: Linux kernel, ASoC (AMD ACP) audio driver. The vulnerable code resides in the AMD ACP ASoC driver (files under sound/soc/amd/).
• Fault: Missing NULL check for chip->chip_pdev in snd_acp_resume(), which can lead to a NULL‑pointer dereference if the ACP platform device was never created. That dereference can cause a kernel oops or crash (availability impact).
• Severity profile: typically rated medium in distribution advisories (example vendor CVSS ~5.5, availability impact). The practical impact is primarily a local‑and‑availability problem rather than remote code execution.

The upstream remedy is minimal and surgical: add a defensive check so the resume path returns cleanly if chip_pdev is NULL, preventing the crash. That sort of fix is low risk to functionality yet critical for robustness on affected hardware families where ACP platform creation can be conditional.

Who is exposed?​

Exposure depends entirely on whether an installed or distributed kernel build contains the affected source lines and whether the runtime configuration and device topology can exercise the problematic path. In practical terms, affected systems will be those that:

• Run a kernel build that includes the AMD ACP ASoC driver code path in question, and
• Run on hardware or VM images where ACP platform device creation could be skipped (making chip_pdev NULL) and then the resume path invoked.

Because kernel sources are reused across distributions and vendor artifacts, the same upstream source file may appear in many different kernels and images. Distributions, OEMs, and cloud vendors commonly backport fixes or ship different kernel versions and CONFIG_* build options, meaning artifact presence must be verified per image, not assumed from a CVE mapping alone.

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What Microsoft’s Azure Linux attestation means — and what it doesn’t​

The attestation: product‑level inventory​

When MSRC says “Azure Linux includes this open‑source library and is therefore potentially affected,” that is a product‑scoped inventory attestation. It signals Microsoft has examined the Azure Linux family (CBL‑Mariner kernels and related artifacts Microsoft distributes under the Azure Linux banner) and found the upstream component present in those builds; as a result Microsoft marks Azure Linux as “potentially affected” in the machine‑readable VEX/CSAF file and the human‑facing CVE entry. Microsoft also pledged to expand those attestations over time and update CVE records if additional Microsoft products are identified as carriers.

What that does not imply​

• It does not prove exclusivity. Azure Linux is the only Microsoft product Microsoes, but that does not mean no other Microsoft product contains the same upstream source. Other Microsoft artifacts — such as WSL2 kernels, linux‑azure kernel builds, Marketplace VM images, appliance images, or vendor‑packaged kernels inside services — may still include the same code until Microsoft inventories them and publishes corresponding VEX entries.
• It does not absolve customers from verifying per‑artifact impact. Because kernel features and drivers ad‑time flags and patch sets, two kernels with similar version numbers may differ in which drivers are compiled in. That means an operator must treat Azure Linux’ attestation as a strong signal to act for Azure Linux instances, and as a prompt to verify other Microsoft artifacts in their estate rather than assume they are unaffected.

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Why attestation rollouts create “known unknowns”​

Microsoft’s shift to machine‑readable CSAF/VEX attestations (started in October 2025) is a transparency win: it enables automation of triage and faster prioritization for customers. But the rollback from “I don’t know” to “I do know” is inherently phased, and that phasing creates transient gaps:

• Big vendors produce a large number of discrete artifacts (kernel builds, images, appliances, cloud images). Inventorying every artifact and mapping it against every upstream CVE is work that occurs over time.
• Product families are often used to represent multiple artifacts (for example, the term “Azure Linux” maps to a set of versions/features and kernel packaging options). A single product attestation addresses that product family, not every separate binary Microsoft may distribute elsewhere.
• Without per‑artifact SBOMs, customers must rely on vendor attestations, their own binary inspection, or both.

For those reasons, Microsoft’s public wording — explicitly promising to update CVE records if additional products are impacted — is both correct and deliberately conservative. Treat a named product as confirmed and others as unverified until shown otherwise.

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Cross‑checking the claim: independent verification sources​

The claim that Azure Linux includes the implicated upstream component and is “potentially affected” can be independently validated in multiple ways:

• The public CVE description and NVD entry document the upstream fix and the affected code path. Use the NVD CVE record for the canonical vulnerability summary.
• Upstream kernel stable commits implementing the null check are recorded in kernel trees and mirrored by OSV and distribution advisories; those commit references let you verify exactly which versions include the fix.
• Major distributions (Ubuntu, Red Hat, Amazon Linux) and vulnerability databases list vendor advisories mapping the CVE to distribution kernel packages and provide updated package versions that contain the patch; those pages serve as practical patching guidance.

Those independent traces — kernel commit, distribution advisories, NVD entries — are the right way to confirm whether a particular kernel image you run includes the patched source or not.

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Practical verification checklist (how to confirm whether a Microsoft artifact you run is affected)​

Below are step‑by‑step checks you can perform on specific Microsoft artifacts to determine whether they include the vulnerable code path.

• Identify the artifact:
• For Azure VMs, note the Azure image name and kernel package version.
• For WSL instances, run uname -a and capture the kernel build string.
• For Marketplace images or appliance images, capture the kernel binary and package metadata.
• Find the kernel version and build ID:
• Run uname -r and inspect /proc/version for build stamps.
• If a distro provides package metadata (rpm, deb), query the package for exact upstream commit IDs or patches.
• Map the kernel to upstream commits:
• Use distribution security notices or OSV entries to map the vendor kernel package name and version to the upstream commit that fixes CVE‑2024‑42074. Distribution advisories often list the fix commit or the patch identifier.
• Inspect for the specific source presence (if you have img/source):
• If you can access kernel sources or a bootable image with /boot and /lib/modules, search the kernel source tree for sound/soc/amd/acp/acp-pci.c and inspect snd_acp_resume() for the null check added by the upstream fix.
• If you only have binaries, compare module versions against a patched build or use binary diffing to detect presence of the patched logic.
• Use vendor VEX/CSAF records:
• Check MSRC’s machine‑readable VEX (CSAF) entry for the CVE to see which Microsoft products have been scanned and what Microsoft’s inventory status is for each product family. Microsoft has committed to updating these entries when additional artifacts are identified.
• If uncertain, assume potentially affected and prioritize patching for safety.

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Prioritization and mitigation guidance​

• Immediate priority: Apply patched kernel packages to all Azure Linux instances identified by the MSRC attestation. Microsoft’s attestation is a direct signal for customers running Azure Linux to prioritize updates.
• Next: Inventory other Microsoft artifacts in your environment (WSL, linux‑azure kernels, marketplace images, appliances) and run the verification checklist above. Treat those artifacts as unverified until you can confirm the presence or absence of the fix.
• Host‑level mitigations: Because this is a kernel NULL‑dereference that primarily impacts availability, defensive steps such as kernel livepatches (if vendor supports them), rolling upgrades, and strict host isolation for untrusted code are helpful stopgaps until full updates are applied. Where livepatch is not available, schedule a kernel upgrade and reboot window as soon as practical.
• Automation: Subscribe to Microsoft’s CSAF/VEX feeds, distribution errata, and third‑party vulnerability feeds (OSV, NVD) so you receive machine‑readable notifications and can automate triage across thousands of artifacts. Microsoft’s move to publish CSAF/VEX is intended to enable exactly this kind of automation.

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Operational risks and tradeoffs​

Strengths of the Microsoft attestation approach​

• Transparency: Publishing a product‑scoped attestation (Azure Linux) is an important, positive step toward vendor transparency and automation of vulnerability triage.
• Actionability: Customers running Azure Linux can rely on Microsoft’s attestation to prioritize patch windows and to schedule remediatiMachine‑readability**: CSAF/VEX feeds enable integration with enterprise vulnerability management tools and SIEM/SOAR pipelines, reducing manual effort.

Remaining risks and limitations​

• Phased coverage means transient unknowns: Microsoft’s attestations are rolled out per product family; large vendors must inventory many artifacts, and until they complete that work, customers operating other Microsoft artifacts have to verify per artifact.
• Per‑artifact build variability: A kernel source file appearing in one product may be omitted or built differently into another Microsoft kernel due to different CONFIG flags, backports, or vendor patches. This makes per‑artifact verification essential.
• Timing gap between upstream fix and vendor patch: Even small fixes can take time to reach packaged kernels in every distribution and product image. During that window, operators must balance availability (applying reboots) and risk exposure.

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Recommendations for enterprise defenders​

• Treat Microsoft’s attestation as a confirmed prompt for Azure Linux remediation and act on it immediately. Use vendor packages and the distro’s kernel update channels to install the official patched kernels.
• Inventory all Microsoft kernel artifacts in your org include:
• WSL2 kernel binaries deployed across developer machines.
• linux‑azure kernels used by managed images / VM scale sets.
• Marketplace images and vendor appliances (which can embed Linux kernels).
• Container host OS images derived from CBL‑Mariner or other Microsoft‑published images.
  Microsoft’s inventory is product‑scoped; your estate may include additional, unverified Microsoft artifacts.
• Automate artifact verification: integrate MSRC CSAF/VEX feeds, distribution advisories (OSV, Ubuntu USN, Red Hat RHSA), and local package inventories into your vulnerability management pipeline. Cross‑reference package versions and upstream commit IDs where available.
• If you cannot immediately patch, apply containment measures: isolate affected hosts, reduce exposure of services (especially local admin paths), and monitor kernel logs/oom/ oops messages to detect crashes.
• Document and test your kernel update and rollback process: kernel reboots are disruptive; rehearsal reduces the blast radius when emergency patching is required.

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Final analysis — what to tell stakeholders​

• To technical owners: Azure Linux is confirmed and must be patched. Microsoft’s attestation is authoritative for Azure Linux and should be actioned now. Use distribution kernel updates or the vendor‑provided images to install the patched kernels.
• To platform owners running other Microsoft artifacts: do not assume you are unaffected. Azure Linux being named does not guarantee other Microsoft kernen; run the per‑artifact verification checklist and prioritize remediation where the vulnerable driver is present.
• To security leadership: Microsoft’s CSAF/VEX rollout is a positive step — but it is a work in progress. Plan for a period of active verification and remediation across Microsoft‑supplied artifacts; allocate resources for per‑artifact checks and ensure automated feeds are integrated into your tooling.

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Conclusion​

CVE-2024-42074 is a straightforward but real kernel robustness fix: a null check in AMD ASoC code to prevent a kernel oops. Microsoft’s MSRC attestation that Azure Linux includes the implicated open‑source library and is therefore potentially affected is an important and actionable signal for Azure Linux customers — but it is not an exclusivity guarantee. Azure Linux is the product Microsoft has publicly inventoried and attested so far; other Microsoft artifacts may still carry the same upstream code until Microsoft cd updates its VEX/CSAF records. Operators must therefore prioritize patching Azure Linux immediately, inventory and verify other Microsoft artifacts in their estate, and integrate machine‑readable vendor attestations and distribution advisories into automated triage pipelines to reduce the “known unknowns” that phased attestations create.

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Source: MSRC Security Update Guide - Microsoft Security Response Center