CVE-2025-37766: Azure Linux AMDGPU DoS and MSRC Attestations

The Linux kernel vulnerability tracked as CVE-2025-37766 — a division-by-zero flaw in the AMD GPU power-management code (drm/amd/pm) — has reignited an important question for Microsoft customers: when Microsoft’s Security Response Center (MSRC) says “Azure Linux includes this open‑source library and is therefore potentially affected,” does that mean Azure Linux is the only Microsoft product that might carry the vulnerable code? The short answer is: no, not necessarily — but the nuance matters. Azure Linux is the only Microsoft product Microsoft has publicly attested as including the implicated component for this CVE at the time of the advisory; other Microsoft-distributed kernel artifacts may also contain the same upstream code and therefore could be affected until they are explicitly inventoried and declared Not Affected or Fixed.

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Background / Overview​

CVE-2025-37766 is a Linux kernel-level issue discovered in the AMDGPU Direct Rendering Manager (DRM) power-management code. The vulnerability arises from improper validation of a user-controlled speed parameter: if a caller supplies a speed value greater than UINT_MAX/8, a division-by-zero can occur. That arithmetic error can crash kernel code paths that manage AMD GPU power features and, in practice, lead to a local Denial-of-Service (DoS) when triggered.
This kind of bug is classified as an availability-impacting kernel issue — it does not, in its public description, enable privilege escalation or data exfiltration, but it can make affected kernels unstable or crash, impacting services and workloads that depend on those machines. Upstream Linux maintainers published fixes and the CVE was recorded and propagated into downstream vendor advisories and tracking databases. Distributions have taken the usual approach: either update kernels to fixed releases or backport the corrective changes into their supported kernel package series.
Microsoft’s public advisory language for this CVE notes that Azure Linux (the Microsoft-maintained Linux distribution formerly known as CBL-Mariner and now referred to by Microsoft as the Azure Linux Distribution) has been mapped to the vulnerable open-source files and is therefore a confirmed product carrier for the affected component. Microsoft also states that it publishes machine-readable CSAF/VEX attestations (beginning October 2025) and that it will update CVE product mappings if further Microsoft products are identified as impacted.

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What Microsoft’s phrasing actually means — a practical reading​

Microsoft’s MSRC wording is precise but conservative:

• When MSRC says “Azure Linux includes this open‑source library and is therefore potentially affected” it is making a product-level attestation: the Azure Linux product family has been inspected and the vendor confirms that the implicated upstream component is present in that product’s build artifacts.
• That attestation is authoritative for Azure Linux — it tells administrators and automated tooling that this Microsoft product ships the component and should be managed accordingly.
• The statement does not constitute a categorical guarantee that no other Microsoft product contains the same upstream files. Microsoft expressly leaves room to expand its product mapping as its internal inventory work continues.

Put plainly: the MSRC text is what was verified so far, not a universal proof of absence across all Microsoft-distributed kernels and images.

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Why Azure Linux may have been named first​

There are practical reasons vendors pick one product to start their attestation work:

• Azure Linux is a single, well-defined product family where Microsoft controls the build pipeline and can quickly produce machine-readable attestations (CSAF/VEX). That makes it a sensible first target for a phased rollout of supply-chain transparency measures.
• Inventorying a sprawling enterprise like Microsoft — with Windows components, cloud VM images, WSL kernels, Marketplace artifacts, and other specialized kernel builds — is nontrivial. A phased approach is normal: attest first the product that’s easiest to verify, then expand.
• Publishing a VEX/CSAF attestation for Azure Linux gives customers clear, machine-actionable data they can use to triage, while Microsoft continues deeper inventory on other artifacts.

This is a strength: Microsoft is public about what it has checked. It’s also a limitation: lack of a public attestation for a product does not equal lack of exposure. Administrators must treat the latter as an operational unknown until product inventories are complete.

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Other Microsoft-distributed kernel artifacts that could carry the same code​

Several Microsoft products and distributions ship or publish Linux kernel artifacts in various forms. Each is a plausible carrier of upstream drivers such as amdgpu (the subsystem that includes drm/amd/pm):

• WSL2 kernel (Windows Subsystem for Linux): Microsoft maintains and publishes a WSL2 kernel source tree and prebuilt kernel images. The publicly available WSL2-Linux‑Kernel repository includes the drivers/gpu/drm subtree and therefore contains the amdgpu sources in the tree used to build WSL kernels. Whether a specific WSL kernel build enables or includes amdgpu depends on kernel configuration and the binary installed on a given host.
• Azure Marketplace images and linux-azure kernels: Microsoft distributes kernel packages and VM images for Azure customers. Azure Marketplace images and some Azure-managed kernel builds can carry vendor kernel packages (linux-azure or other custom builds) that may include the amdgpu driver.
• AKS node images and managed node OS images: Node images used for Kubernetes in Azure may include kernel packages or modules that re-use the upstream driver sources.
• Other Microsoft-provided Linux artifacts: Custom kernel images for appliances, specialized device offerings, or internal host images.

In short, any Microsoft product or image that ships a Linux kernel build that includes the drivers/gpu/drm/amd source path could include the same vulnerable code until proven otherwise.

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Technical verification: how to determine if your systems are actually affected​

Vulnerability presence is a build-time and configuration-time property. A kernel build may contain the source for amdgpu but still be not vulnerable if the build configuration disables the offending code or if the kernel version already contains the upstream fix. Conversely, a kernel that includes amdgpu and is older than the fixed upstream releases (or lacks vendor backports) will be vulnerable.
To determine exposure, perform these checks on each host, VM, or product artifact under your control:

• Identify the kernel version:
• Run: uname -r
• Map the kernel version to vendor advisories and the upstream fix list to determine whether the kernel release contains the corrective commits or if a backport is available.
• Check whether the amdgpu driver is present on the system:
• Inspect installed modules: lsmod | grep -i amdgpu
• Check module files: ls /lib/modules/$(uname -r)/kernel/drivers/gpu/drm/amd
• Search for driver sources in custom kernel trees or build artifacts (for images you control).
• Confirm whether the driver is built-in, modular, or absent:
• If amdgpu is compiled into the kernel (not a module), lsmod won’t show it; check kernel config: zcat /proc/config.gz | grep -i 'AMDGPU' (if /proc/config.gz is available)
• If it’s a module, see if it’s loaded and whether devices are using it.
• For WSL2:
• Check the WSL kernel version: inside WSL run uname -r
• On the Windows host, run: wsl --status and wsl --update to learn and control the WSL kernel image.
• If your WSL kernel is an older WSL-managed build that predates the upstream fix, treat it as potentially vulnerable.
• For Azure VM images:
• Check which kernel package the image uses (e.g., linux-azure, distro kernels).
• Consult vendor/Ubuntu/Debian/SUSE/Red Hat security advisories mapping fixed kernel package versions to the upstream commits.
• When in doubt, assume local privilege is required to trigger the issue (upstream CVE indicates a local attack vector), but do not dismiss the impact: a local user or a workload capable of invoking the path may cause a service crash or reboot.

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Immediate mitigation and remediation guidance​

If you manage Linux hosts (including those running on Azure, inside WSL, or as part of Microsoft-provided images), follow a prioritized plan:

• Immediate triage (fast, low-effort):
• Inventory all Microsoft-distributed kernels and images you run (Azure Marketplace images, WSL instances, managed node images).
• Determine kernel versions with uname -r and match them to vendor advisories; if your kernels are older than the fixed versions or vendor updates aren’t available, plan remediation.
• For WSL: run wsl --update on Windows hosts to ensure the WSL kernel is the latest Microsoft-provided build. If you run a custom WSL kernel, rebuild it against a fixed kernel baseline.
• Short-term remediation:
• Apply vendor-supplied kernel updates or patches as soon as they are available from your OS vendor (Ubuntu, Debian, SUSE, Red Hat, Azure Linux, etc.). Prefer vendor-supplied packages/backports — they carry distribution-specific fixes.
• Reboot or reload kernels/modules as required to ensure the fixed code becomes active.
• Compensating controls (where immediate patching isn’t possible):
• Restrict access to systems with AMD GPUs: limit local accounts and untrusted workloads that might invoke the vulnerable sysfs or driver paths.
• Use process sandboxing and strict access controls to prevent untrusted users from interacting with GPU power-management interfaces.
• Monitor logs (dmesg, kernel logs) for unexplained GPU-driver crashes or kernel oops messages relating to amdgpu.
• Long-term:
• Adopt an inventory-driven approach: track which product artifacts include which upstream components. Use machine-readable VEX/CSAF attestations where vendor-provided (Microsoft is publishing these for Azure Linux and plans to expand).
• Integrate kernel version mapping into your patch-management and vulnerability-triage systems: automate the mapping from kernel version → upstream commit → vulnerability status.

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Practical detection commands and checks (copy-paste friendly)​

• Check kernel version:
• uname -r
• Check for amdgpu module presence:
• lsmod | grep -i amdgpu
• ls /lib/modules/$(uname -r)/kernel/drivers/gpu/drm/amd || true
• Check kernel config for AMDGPU:
• if [ -r /proc/config.gz ]; then zcat /proc/config.gz | grep -i AMDGPU || true; fi
• Review kernel logs for AMDGPU crashes:
• dmesg | grep -i amdgpu
• journalctl -k | grep -i amdgpu
• WSL specific:
• wsl --status
• Inside WSL: uname -r
• On Windows host: wsl --update (updates the Microsoft-managed WSL kernel)

These checks will tell you whether the driver is present and whether a given kernel version might fall into a vulnerable range — they do not replace the definitive step of patching to an explicitly fixed kernel release.

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Why relying solely on a single-vendor statement can be risky​

Microsoft’s product attestation is useful and necessary, but it represents a point-in-time inventory result for the product family in question. There are pragmatic reasons to avoid treating a single statement — “only Azure Linux is affected” — as a full security guarantee:

• Microsoft ships multiple kernel artifacts; the presence of an upstream driver tree in a kernel source repo means a product could be affected depending on selection of config options and the exact kernel version built.
• A vendor may publish VEX/CSAF attestations in phases; a product may be “under investigation” or simply not yet mapped rather than definitely Not Affected.
• Cloud and container environments can inherit kernels from multiple layers: host kernel, guest kernel, container runtime, and image packages. Each layer must be examined.
• Automated scanning tools that flag CVEs against a vendor product often operate on package names or component presence; without machine-readable attestations, such tooling produces false positives or misses edge cases. Microsoft’s VEX effort helps reduce that noise — but only once the vendor attests coverage for each product.

In short: treat vendor attestations as authoritative for the products they cover, but continue to verify artifacts that you run — especially for infrastructure and images Microsoft distributes that are not yet enumerated in the VEX output.

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Strengths and risks of Microsoft’s CSAF/VEX approach​

Strengths:

• Machine-readable attestations (CSAF/VEX) reduce ambiguity: defenders can automate triage and quickly determine whether a specific product SKU is affected.
• Transparency for Azure Linux helps customers who run that distro make fast, risk-based decisions.
• A clear update path: Microsoft has committed to updating CVE product mappings as additional artifacts are verified.

Risks and limitations:

• Phased rollout leaves windows of uncertainty for other Microsoft-hosted kernel artifacts (WSL kernels, Azure VM kernel images, Marketplace appliances) until they are explicitly attested.
• Operational inventory burden still rests with customers: even with VEX, organizations must apply the attestation data to their specific deployed artifacts.
• Potential for misinterpretation by consumers who read the language as a categorical absence of risk across Microsoft’s entire ecosystem.

Overall, the approach is constructive and aligns with industry movements toward machine-readable vulnerability attestations. But operational rigor is still required at the customer end.

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What security teams should tell their stakeholders (short brief for execs)​

• The company should treat CVE-2025-37766 as a moderate-severity kernel DoS risk for Linux systems that include the amdgpu driver and run vulnerable kernel versions.
• Microsoft’s public attestation confirms Azure Linux is a confirmed product carrier; other Microsoft kernel artifacts may still be unverified and should be checked.
• Action: inventory affected hosts, patch kernels with vendor-supplied fixes, and update WSL kernels and any Azure-hosted images to patched kernels. If patching is delayed, apply compensating access controls for GPU management interfaces and monitor for kernel crashes.
• Visibility is improving: Microsoft now publishes CSAF/VEX attestations (starting with Azure Linux as a phased rollout), which will make future triage faster — but don’t assume the absence of a VEX entry equals safety.

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Recommended checklist (operational steps, prioritized)​

• Inventory: List all Linux kernels running in your environment, including WSL instances and Azure VM images.
• Map: Cross-check kernel versions against vendor advisories and the upstream fix list to identify unpatched kernels.
• Patch: Apply kernel/security updates from your OS vendor or from Microsoft-managed channels (for WSL and Azure images).
• Verify: Reboot into patched kernels or reload fixed modules and confirm absence of kernel oopses relating to amdgpu.
• Compensate: If immediate patching is impossible, restrict local access and isolate vulnerable hosts from untrusted workloads.
• Automate: Integrate vendor VEX/CSAF outputs into your vulnerability management pipeline as they become available.
• Monitor: Add kernel oops alerts and GPU-driver crash detection to your host monitoring.

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Final analysis and takeaways​

CVE-2025-37766 is a textbook example of a kernel-level availability bug that is serious enough to matter for production systems but does not, in its public description, enable remote code execution or privilege escalation. Microsoft’s advisory that Azure Linux includes this open-source library and is therefore potentially affected is an important and correct disclosure: it tells customers exactly which Microsoft product has been confirmed to contain the upstream code implicated by the CVE. However, it is not a global exclusionary statement: Microsoft’s inventory work is ongoing, and other Microsoft-distributed kernel artifacts (notably the WSL2 kernel sources and some Azure kernel images) can and do contain the same upstream driver paths, meaning they are plausible carriers until proven otherwise.
For operations and security teams, the practical response is straightforward: inventory, patch, and verify. Use Microsoft’s evolving CSAF/VEX attestations when they are available to accelerate triage, but do not supplant artifact-level verification with a single-vendor statement alone. Finally, treat WSL kernel images and Azure VM images as first-class artifacts in your vulnerability scanning and update workflows — they are part of your attack surface and should be treated as such.
CVE-2025-37766 is fixable through kernel updates and conservative configuration; the combination of vendor attestations plus active patch management will keep systems resilient. The most important thing right now is to act on facts in your environment: identify where amdgpu is present, determine whether those kernels have the upstream fixes or vendor backports, and bring affected systems to patched kernel releases as your risk posture and operational constraints allow.

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Source: MSRC Security Update Guide - Microsoft Security Response Center