CVE-2024-39481: Azure Linux Attestation and Microsoft Product Coverage

Microsoft’s MSRC entry for CVE-2024-39481 names the Linux kernel media controller fix (“media: mc: Fix graph walk in media_pipeline_start”) and explicitly calls out Azure Linux as a Microsoft product that “includes this open‑source library and is therefore potentially affected,” but that statement is a product‑scoped attestation — not a technical proof that no other Microsoft product could contain the same vulnerable code. ([msrc.microsoft.cosoft.com/update-guide/vulnerability/CVE-2024-39481/))

Background / Overview​

CVE-2024-39481 is a Linux kernel vulnerability affecting the media controller (mc) code. The bug arises because a graph-walking routine in media_pipeline_start attempts to follow link types that are not data links; in particular, ancillary link types can cause the walk to dereference unexpected structures and crash the kernel. The root cause was fixed upstream by restricting the walk to MEDIA_LNK_FL_DATA_LINK links only. The defect has been cataloged across standard vulnerability trackers and distribution advisories and is classified as a local denial‑of‑service (availability) issue with a medium CVSS score (CVSS v3 ~5.5).
Multiple mainstream Linux distributions released kernel updates that include the upstream fix. For example, Ubuntu’s kernel update packages reference the same fix and list CVE‑2024‑39481 among the patches backported into the linux‑azure and related kernel builds; SUSE, Debian, and other distributors have similar advisories. Distribution changelogs also point to the stable‑tree commits that implement the fix. These independent vendor advisories confirm the technical description and that patched kernels are being rolled into distribution kernels.

---

Short answer to the question​

• Is Azure Linux the only Microsoft product that includes the implicated open‑source library and is therefore potentially affected?
• No — Azure Linux is the only Microsoft product Microsoft has publicly attested to include the implicated upstream component for this CVE so far, but that attestation is intentionally scoped. It is an inventory statement for the Azure Linux images Microsoft builds and publishes, not an exclusivity guarantee for all Microsoft artifacts. Other Microsoft-distributed kernels, kernel builds, or images could still contain the sanding on the kernel version and build configuration; absence of a public attestation does not prove absence of exposure.

---

Why Microsoft names Azure Linux (and what that naming actually means)​

Microsoft’s recent transparency effort — the phased rollout of machine‑readable CSAF/VEX attestations that began with Azure Linux in October 2025 — explains the messaging style you see on MSRC CVE pages. The company is deliberately starting its VEX/CSAF disclosures with the Azure Linux distribution because it is the Microsoft‑maintained Linux image family used widely in Azure. That allows MSRC to provide authoritative, machine‑readable attestations for a known set of artifacts first, then expand coverage to other products over time. The MSRC blog explains that this rollout is intentional and phased.
This operational choice creates two practical implications for defenders and asset owners:

• When MSRC says “Azure Linux includes this open‑source library and is therefore potentially affected,” that phrase is a helpful, authoritative indicator for customers who run Azure Linux images — treat it as gospel for those images.
• When a Microsoft product is not listed, that absence is not equivalent to “not affected”; it often simply means that particular Microsoft artifact has not yet been inventoried and attested under the VEX program. In short: the attestation is one step in a discovery process, not the final sweep of all Microsoft SKUs.

---

Technical verification: what the CVE actually is and how serious it is​

CVE-2024-39481’s technical description and the upstream fixes are well documented in multiple independent databases and distribution advisories.

• The vulnerability is a logic/validation error in the media controller graph-walk code that lets the kernel follow non‑data links and crash; the upstream fix restricts the walk to MEDIA_LNK_FL_DATA_LINK links. This changes the walk condition and prevents the crash.
• Attack vector: local. Privilege required: low. Impact: Availability (kernel crash/DoS). CVSS v3.1 score around 5.5 (medium). Exploitation requires local access; it is not a remote code execution zero‑day in the sense of network‑triggered arbitrary execution.
• Kernel ranges noted by vendor trackers identify the affected upstream series where the vulnerable code was present prior to the stable backports. Distribution advisories list the patched package versions customers should install.

Taken together, these independent confirmations (OSV/NVD/Ubuntu/SUSE/distribution changelogs) corroborate the technical root cause and that maintainers have produced patches. That cross‑corroboration is important because it ties the CVE entry to concrete upstream commits and distribution packages, making remediation straightforward for most

---

Why attestations name a product but can’t prove exclusivity​

There are several practical reasons Microsoft’s Azure Linux attestation should not be read as an exclusivity guarantee:

• Kernel artifacts are built per‑image: whether a given Microsoft image includes the vulnerable code depends on the exact upstream commit range, the kernel version, and the build-time configuration (CONFIG_* flags) used when the kernel was built. A feature such as the media controller may be compiled out of some kernels entirely. That means two Microsoft artifacts that both call themselves “Linux” might differ in whether they include the vulnerable path.
• Microsoft publishes VEX/CSAF attestations by product/artifact and in phases. Starting with Azure Linux, MSRC is building artifact inventories and publishittestations; as the program matures, Microsoft will add attestations for other product families. Until Microsoft publishes an explicit “Not Affected” or “Known Affected” VEX assertion for a particular Microsoft product, defenders should treat that product as “not yet verified” rather than “safe.”
• Microsoft operates a very large, heterogeneous portfolio (cloud images, marketplace VM images, WSL kernels, edge/IoT builds, custom device firmware). Each of those artifacts may use different kernel trees or vendor backports. Only artifact‑level verification (inspecting the shipped kernel binary, build metadata, or published VEX/CSAF for that SKU) yields definitive answers.

---

Practical steps for defenders: how to verify whether your Microsoft‑supplied artifact is affected​

If your environment uses Microsoft artifacts — cloud VM images, WSL, Azure Kubernetes nodes, or Microsoft‑published container images — don’t rely solely on the MSRC page naming Azure Linux. Verify artifact‑by‑artifact using this checklist.

• Identify the artifact(s) you run:
• Azure VM image SKU, WSL2 kernel, Azure Stack/IoT image, marketplace image, or a Microsoft‑managed container host.
• Determine the kernel version and build metadata:
• On a running Linux host: uname -r
• Find the kernel package version via dpkg -l | grep linux-image or rpm -q kernel
• If /proc/config.gz is available: zcat /proc/config.gz | grep CONFIG_MEDIA
• Check for presence of the media controller and related config options:
• grep -i media /boot/config-$(uname -r) or zcat /proc/config.gz | grep MEDIA
• lsmod | egrep 'v4l2|media|mc'
• If the media controller is not built (CONFIG_MEDIA_CONTROLLER=n) then the specific mc graph-walk path may not be reachable in that artifact.
• Cross-reference kernel version against known affected ranges:
• Consult the CVE’s tracker entries and distribution advisories to map the vulnerable commit ranges to kernel versions (for example, distribution trackers list the patched package versions to install).
• Inspect the binary for the affected symbol or verify upstream commit inclusion (for advanced teams):
• Where available, compare the artifact’s kernel git commit id (often exposed in /proc/version or package changelog) to the upstream commit ranges cited by OSV or by the stable kere artifact’s kernel predates the fix, treat it as affected.
• Remediate and verify:
• Apply the vendor/kernel updates provided for the product (e.g., install the updated linux-image-azure packages for Azure VM images) and reboot when the kernel is updated.
• For WSL images or other Microsoft-shipped kernels, watch for MSRC VEX/CSAF entries or product advisories stating “Fixed” or “Not Affected.”

These steps give a deterministic answer: either the artifact contains the vulnerable code (and needs patching), or it does not (because the feature was not compiled in or the kernel commit already contains the fix).

---

Specific Microsoft artifacts to check first (if you run Microsoft infrastructure)​

• Azure Linux images (MSRC attests these images already). Prioritize these for patching; MSRC’s attestation is authoritative for this artifact family.
• Linux-azure kernel builds used in certain official Azure images or optimized kernels (these are often the kernel packages updated by Ubuntu’s linux-image-azure releases). Distribution advisories map the necessary package updates.
• WSL2 kernel images shipped with Windows updates or downloadable WSL kernels: WSL kernels are distinct artifacts and can be built from different kernel trees — check the kernel build ID embedded in the WSL kernel you run.
• Custom Microsoft‑managed appliances (Azure marketplace appliances, Windows components that embed Linux kernels for container hosts, IoT/edge images): these require explicit inventory validation because they may use vendor-patched or customized kernel trees.

---

Operational recommendations and mitigations​

• Patch priority: treat CVE‑2024‑39481 as a local DoS risk — prioritize patching for systems exposed to untrusted local users (multi‑tenant VMs, developer machines with untrusted code, container hosts where container users have some access to the kernel).
• Reboot windows after kernel updates: kernel fixes require reboot to take effect.
• For hardened environments where patching is slow:
• Limit local access and user accounts that can exercise media graph operations.
• Use mandatory access controls and containerization so that untrusted workloads cannot directly trigger local kernel paths.
• Monitor dmesg and system logs for media subsystem crash signatures after the vendor patch is applied to detect regressions or partially mitigated systems.
• For servicenventory: enumerate which SKUs and images your tenants run and prioritize the Azure Linux images MSRC listed, then extend artifact-level checks to other Microsoft-supplied kernels.
• Automate detection: build scripts that collect uname -r, /proc/version, and kernel config fragments and compare to known affected ranges; integrate this into your patch-management dashboard.

For clarity: these mitigations reflect the technical characteristics of the bug (local, low‑privilege required, availability impact) and the practical realities that Microsoft and distribution vendors publish patches and advisories; they are not suggestions that a remote‑exploitable RCE exists for this CVE.

---

What Microsoft’s wording promises — and its limits​

Microsoft’s MSRC wording that “Azure Linux includes this open‑source libraryntially affected” serves two purposes:

• It gives Azure Linux customers immediate, actionable intelligence: you run the attested artifact; check and patch it now.
• It establishes a starting point for Microsoft’s planned VEX/CSAF coverage of other products; MSRC has explicitly said it will update CVE pages and machine‑readable attestations if additional Microsoft products are later found to ship the same upstream component. That promise is important operationally: if Microsoft later discovers that a WSL kernel or another internal build ships the same code, MSRC will update the CVE mapping.

But the wording also deliberately avoids a global claim of exhaustive scanning. The technical reality of product heterogeneity — many SKUs, custom kernel trees, and differing compile-time flags — makes a single-line exclusivity statement scientifically unsound until artifact-level inventories are complete. Security teams therefore must combine the MSRC attestation with their own artifact verification for other Microsoft-supplied components.

---

How to read MSRC CVE pages going forward (short guide)​

• If MSRC names a Microsoft product in a CVE entry, treat that name as an autn for that product family.
• If MSRC does not name a Microsoft product, do not assume the product is safe — it may simply be “not yet attested.” Treat the absence as “not yet checked” rather than “not affected.”
• Consult the MSRC CSAF/VEX JSON files for machine‑readable attestations where available (MSRC began publishing these in October 2025). The VEX file for a CVE contains explicit per‑product assertions: Not Affected / Known Affected / Fixed / Under Investigation. Use these to automate impact triage.

---

Analytical takeaway: what this means for risk teams​

• For defenders running Azure Linux images, MSRC’s statement is the clearest signal you need: apply the patched linux-image packages Microsoft or your distribution vendor provides and reboot. Vendor advisories and distribution changelogs already list patched package versions.
• For defenders running other Microsoft artifacts, treat the MSRC attestation as a signpost, not a clearance. Perform artifact‑level discovery and verification on your Microsoft‑supplied kernels (WSL, marketplace images, custom Azure images, container host kernels) before concluding you are not affected.
• For security automation vendors and SOC teams: integrate VEX/CSAF ingestion, but keep fallback artifact checks (uname, /proc/version, kernel config) as a secondary verification mechanism. Microsoft’s phased VEX rollout is helpful, but it will take time to encompass the full product portfolio.

---

Final verdict and guidance​

Microsoft’s public statement for CVE‑2024‑39481 that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate and authoritative for the Azure Linux images Microsoft maintains. It is not, however, a blanket assurance that no other Microsoft product contains the vulnerable code. Microsoft’s phased CSAF/VEX rollout, which began with Azure Linux in October 2025, is the reason you will often see Azure Linux named first; MSRC has committed to updating CVE records if additional Microsoft products are identified as carriers. Until such attestations are published for other SKUs, organizations must perform artifact‑level verification across their Microsoft-supplied images and kernels. (msrc.microsoft.com)
Action checklist (immediate):

• Patch and reboot all Azure Linux images in your environment as a priority.
• Run the artifact verification checklist on all Microsoft-supplied kernels you use (WSL, marketplace images, managed container hosts).
• Ingest MSRC CSAF/VEX feeds (where available) and correlate with your asset inventory to automate triage.

CVE‑2024‑39481 is consequential for availability on affected builds; Microsoft’s Azure Linux attestation gives a clear remediation priority. But do not treat the attestation as exclusive — treat it as a starting point for a deterministic, artifact‑level verification process across your entire estate.

---

---

Source: MSRC Security Update Guide - Microsoft Security Response Center