Azure Linux and CVE-2024-45006: Microsoft Attestations and Kernel Risk

Microsoft’s published advisory for CVE-2024-45006 confirms that the vulnerable code is an upstream Linux kernel xHCI bug and that Azure Linux is the Microsoft product Microsoft has identified so far as “including this open‑source library and therefore potentially affected,” but that public attestation is a scoped inventory statement — not an assurance that no other Microsoft product could carry the same kernel code.

Background / Overview​

CVE‑2024‑45006 is a Linux kernel vulnerability in the xHCI USB host controller driver that can trigger a NULL pointer dereference during re‑enumeration of full‑speed USB devices after a failed address assignment. The bug is rooted in the Panther‑point xHCI handling path: when an address device command fails, a new xhci_virt_device structure can be allocated while the controller’s bandwidth table pointers remain uninitialized. A subsequent usb_ep0_reinit() call may then cause xhci_configure_endpoint() to dereference those invalid pointers, producing a kernel crash (an OOPS or panic).
The upstream Linux stable patch series and distribution advisories show the fix was applied to the kernel stable trees; maintainers included the patch in vendor kernels and distribution security updates. The patch series entry and stable update notes document the exact change and the kernel function involved (xhci_reserve_bandwidth / xhci_configure_endpoint).
From a risk perspective the vulnerability has a medium technical severity (CVSS 3.1 base ≈ 5.5 as reported by NVD and multiple distro trackers) and is an availability‑impact bug: exploitation causes a local kernel NULL pointer dereference and denial of service. The attack vector is local: an attacker would need to cause (or simulate) the precise USB re‑enumeration sequence on a system with the affected kernel and relevant xHCI configuration. That said, in multi‑tenant or automated provisioning environments (cloud hosts, VM images, container hosts) a local fault can still translate to operational impact for many users if unpatched kernels are in broad use.

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What Microsoft actually said — and why that wording matters​

Microsoft’s Security Response Center (MSRC) CVE pages for Linux kernel CVEs follow a consistent pattern: they publish product‑level attestations (CSAF/VEX) stating which Microsoft product(s) include the upstream component and are therefore potentially affected, and they commit to update those records if further Microsoft products are identified. The wording used by MSRC — for example on CVE entries including the FAQ line “Is Azure Linux the only Microsoft product that includes this open‑source library...?” followed by the explanation about CSAF/VEX and updates — is explicit that Azure Linux is the product Microsoft has inventory‑checked so far, and that Microsoft will expand its attestations as inventory work completes. ([archive.vn](https://archive.vn/2025.12.07-22030...com/update-guide/vulnerability/CVE-2024-50217
Two practical takeaways from Microsoft’s phrasing:

• When MSRC says “Azure Linux includes this open‑source library and is therefore potentially affected,” that is an authoritative, product‑scoped inventory statement: Azure Linux customers should treat the product as in‑scope and take remediation actions based on the vendor‑listed status.
• That same statement, however, does not mean Microsoft is declaring other Microsoft products to be unaffected. The absence of an attestation for other products is generally an indication that Microsoft has not yet completed or published the inventory mapping for those other artifacts — it is not evidence of absence. In short: Azure Linux = confirmed to be in scope; other Microsoft artifacts = unknown unless/until Microsoft publishes their status.

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Short answer to the user question​

No — Azure Linux is not necessarily the only Microsoft product that could include the vulnerable open‑source kernel code. It is the only Microsoft product Microsoft has publicly attested (so far) to include the implicated upstream component for CVE‑2024‑45006. That attestation is authoritative for Azure Linux customers, but it is not a categorical exclusivity guarantee for the entire Microsoft product ecosystem. Microsoft has explicitly said it will update the CVE/VEX record if additional Microsoft products are discovered to include the component.

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Why other Microsoft products could plausibly carry the same code​

The vulnerable code sits in upstream Linux kernel sources (drivers/usb/host/xhci.c). Any Microsoft product that ships a Linux kernel build derived from a kernel version containing the vulnerable commit range — and that build includes xHCI support for the Panther‑point code path — could, in principle, include the same defect until patched. Important examples:

• Azure Linux (the product MSRC attested) — Microsoft’s own Linux distribution (formerly CBL‑Mariner lineage) that Microsoft builds, maintains, and runs across Azure infrastructure. MSRC’s CSAF/VEX rollout started by inventorying this product family. Azure Linux is therefore a confirmed carrier pending patches.
• The WSL2 kernel that Microsoft ships for Windows Subsystem for Linux (WSL) — Microsoft builds and distributes a Linux kernel for WSL, publishes the source, and actively maintains kernel releases for WSL2. That kernel repository contains drivers from the upstream tree and is shipped to millions of Windows machines as part of WSL2 updates. Whether a particular WSL kernel binary is vulnerable depends on the kernel version and whether the specific xHCI code path and commit range are present in the WSL kernel build. Because Microsoft builds and ships kernels for WSL, this artifact is plausibly a carrier until verified.
• Other Microsoft‑hosted Linux artifacts and images — examples include kernel images used for Azure VM host tooling, Marketplace images, container host images (AKS), and any Microsoft automation pipeline that builds or republishes distro kernels for cloud service use. These artifacts often derive from the same upstream sources or vendor trees and therefore can carry upstream fixes (or lack them) in lockstep.
• Historically Microsoft has maintained CBL‑Mariner (now rebranded and part of the Azure Linux lineage) and used it across many Azure services; that heritage means the same kernel subsystems can transitively appear in multiple runtime artifacts. Microsoft’s decision to start VEX/CSAF with Azure Linux was deliberate because it’s the most practical initial target for product‑level inventory.

All of the above explains why the MSRC FAQ is careful: Azure Linux = confirmed, but other Microsoft products may also be carriers until Microsoft completes inventory and declares Not Affected or Fixed via VEX/CSAF updates.

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Technical validation and cross‑references​

To validate and cross‑reference the core facts:

• Upstream technical description and severity are recorded in public trackers (NVD, OSV, vendor advisories) which describe the Panther‑point xHCI NULL dereference and show CVSS scoring and distribution fix status. These independent trackers confirm the problem description and impact.
• The upstream stable kernel patch series included the fix for the xHCI path (the stable patch notes reference the change to xhci_reserve_bandwidth / xhci_configure_endpoint), and distribution errata entries map that patch into vendor kernels. These are the authoritative sources for where the fix was applied in the kernel stable branches.
• Microsoft’s transparency blog posts document the CSAF and VEX rollout timeline: Microsoft published machine‑readable CSAF files in late 2024 and began publishing VEX attestations for Azure Linux in October 2025 as part of a phased approach. That operational timeline explains why many MSRC CVE pages include the same FAQ wording about Azure Linux and about updating CVE records if additional product impact is found.
• Multiple distribution security trackers (Alpine, Red Hat, Ubuntu, Amazon Linux advisories) list CVE‑2024‑45006 and show which distro kernels received backports or fixes. That distribution telemetry is the practical mechanism operators use to patch running systems.

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Practical detection and mitigation guidance for administrators​

If you manage Linux images, Azure resources, or Windows hosts running WSL, follow a prioritized, defensible remediation plan. The following steps are practical, repeatable, and structured for rapid triage.
1.) Confirm Microsoft’s attestation status for your product inventory

• Treat MSRC’s VEX/CSAF listing that names Azure Linux as authoritative for Azure Linux images. If you run Azure Linux, treat the product as in scope and follow vendor/supported update channels.

2.) Inventory kernel artifacts and images across your estate

• Identify systems running Azure Linux images (AKS node pools, container hosts, Azure VM images built from Azure Linux).
• Identify instances where Microsoft‑supplied kernels are used (WSL2 kernels on Windows clients/servers, Marketplace images, kernel images baked into appliances). Use configuration management and image inventories to list kernel artifacts and their build sources.

3.) Check kernel versions and whether the patch is applied

• On Linux hosts, run:
• uname -sr (to get kernel version)
• zgrep XHCI /boot/config-* or grep CONFIG_USB_XHCI /proc/config.gz (to confirm that xHCI support is built)
• Examine distro security notices for CVE‑2024‑45006 and the fixed kernel package versions for your vendor.
• For WSL2, check the WSL kernel version Microsoft shipped (the WSL kernel repo and release notes reveal version numbers) and follow Microsoft’s WSL update guidance (Windows Update / WSL package updates).

4.) Prioritize patching by exposure and business impact

• High priority: multi‑tenant hosts, cloud images used by many customers (AKS, shared container hosts), and automated image builders that produce many downstream artifacts.
• Medium priority: single‑tenant VMs and developer machines that use WSL; treat them as lower blast radius but still patch in a timely manner.
• Low priority: devices that don’t expose the relevant xHCI Panther‑point path (e.g., kernels built with xHCI disabled), but verify via kernel config rather than assume.

5.) Monitor logs and look for OOPS signatures

• The kernel OOPS signature in public reports includes references to xhci_reserve_bandwidth or similar xHCI call sites and a NULL pointer dereference at a small fixed offset. Hunt for kernel oops/traces in system logs (journalctl, /var/log/messages) that reference xhci or USB re‑enumeration failures. Use centralized logging to search historically across the fleet.

6.) Mitigations if patching is delayed

• Where immediate patching is impossible, reduce attack surface: avoid exposing untrusted processes to the host’s USB stack (isolation, disable USB passthrough in VMs, restrict untrusted device attachments). These measures do not “fix” the bug but reduce the likelihood of someone triggering the precise local re‑enumeration sequence on a production host. Note: in many cloud scenarios, physical USB attach is unlikely; the bigger risk is for bare‑metal or edge devices and developer workstations.

7.) Keep attending to Microsoft VEX/CSAF feeds and distributor advisories

• MSRC has committed to publishing VEX attestations and updating CVE pages if additional Microsoft products are dihe component. Consume MSRC CSAF/VEX outputs and your distribution vendor’s security tracker for canonical patch versions and timelines.

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Detection playbook snippets (examples)​

• Check kernel version:
• uname -r
• Confirm xHCI support is present:
• grep -i xhci /boot/config-$(uname -r) || zgrep CONFIG_USB_XHCI /proc/config.gz
• Search logs for xHCI OOPS signatures:
• journalctl -k | grep -i xhci
• grep -i 'reserve_bandwidth' /var/log/messages*

These simple checks let you quickly map which images/hosts in your fleet deserve immediate action.

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Risk analysis — strengths, limits, and potential pitfalls​

• Strength: Microsoft’s phased, machine‑readable VEX/CSAF rollout is a major transparency improvement. By publishing explicit attestations for Azure Linux and promising updates, Microsoft reduces noisy, false‑positive triage for customers who run Azure Linux images. For Azure Linux customers, the Microsoft statement is an authoritative, actionable signal.
• Limit: Product‑scoped attestations are not exhaustive. Large vendors cannot instantly inventory every single downstream artifact, and many Microsoft teams ship Linux kernels in varied forms (WSL kernels, Azure images, container hosts). The attestation therefore reflects inventory progress rather than a complete exclusion of other product carriers. Security teams should not interpret the Az as a blanket “other Microsoft products are safe.”
• Operational pitfall: automation that blindly filters CVEs by vendor attestation may miss vulnerable Microsoft artifacts that have not yet been publicly attested. A prudent enterprise CSIRT should treat an MSRC product‑level “Not yet listed” as “not yet verified” and combine vendor attestations with independent artifact inventory and kernel config checks.
• Residual uncertainty: determining whether a particular Microsoft artifact is vulnerable often depends on kernel version, the commit/patch set applied, and kernel configuration (which drivers and code paths were built in). This makes automated assessments nontrivial without direct artifact inspection or vendor‑supplied VEX data for each artifact.

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Recommended actions for Microsoft and customers​

For Microsoft (recommended best practices)

• Continue the VEX/CSAF rollout beyond Azure Linux and publish attestations for other kernel artifacts Microsoft builds and ships (WSL kernels, Marketplace kernels, AKS node images, and any host kernels used inside Azure management planes).
• Where practical, publish per‑artifact kernel build metadata (kernel version, config flags, commit ranges) so downstream customers can automate impact determinations.
• Maintain a clear cadence for updating VEX entries and flagging “Under investigation” artifacts to reduce customer uncertainty.

For customers (immediate steps)

• If you run Azure Linux: patch promptly using Microsoft’s delivered updates for Azure Linux images (treat MSRC attestation as actionable).
• If you run WSL2 or other Microsoft‑supplied kernels: check WSL kernel versions and apply Microsoft’s WSL updates or Windows updates that include WSL kernel updates.
• For all Linux servers and images: verify kernel versions, check for the distribution patch that closes CVE‑2024‑45006, and update host images and golden images used by provisioning pipelines.
• Treat “no attestation” from MSRC as “not yet verified”; perform your own artifact checks for any Microsoft kernels you rely upon.

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Conclusion​

CVE‑2024‑45006 is a real, upstream Linux kernel xHCI NULL pointer dereference with a documented upstream fix. Microsoft’s public advisory and VEX/CSAF work correctly call out Azure Linux as a product that includes the affected open‑source component — and they commit to update records if other Microsoft products are later identified as carriers. That statement is authoritative for Azure Linux users, but it is not a global, product‑scope guarantee that other Microsoft artifacts are free of the code. Security teams must therefore combine MSRC VEX attestations with independent artifact inventory and proactive patching of any Microsoft‑managed kernels they consume (WSL, Marketplace images, container hosts, Azure node images, etc.).
Treat Microsoft’s attestation as a starting point for triage: patch Azure Linux immediately where used, verify kernel builds for WSL and other Microsoft‑supplied artifacts, and monitor MSRC’s evolving VEX/CSAF data for updates. If you need to prioritize work across a large estate, focus first on shared/cloud‑facing images and orchestration hosts where a local kernel denial‑of‑service has the largest operational blast radius. The combination of vendor VEX data plus your own artifact checks will keep you both accurate and resilient against surprises.

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Source: MSRC Security Update Guide - Microsoft Security Response Center