CVE-2025-38011: Azure Linux Attestation and AMDGPU Risk Explained

Microsoft’s brief advisory that “Azure Linux includes this open‑source library and is therefore potentially affected” is accurate — but it is a product‑scoped attestation, not a categorical statement that no other Microsoft product could include the same vulnerable kernel code.

Background / Overview​

CVE‑2025‑38011 is a Linux kernel issue in the AMD GPU driver area (drm/amdgpu) where a code path that unmaps a CSA structure and frees a GPU VM used a lock that could be interrupted by signals, resulting in memory leakage and warning backtraces. The upstream fix converts the wait to an uninterruptible wait to avoid the abort-and-leak behavior. This is an availability/robustness fix rather than a remote code execution or privilege‑escalation patch. The practical symptom is kernel warnings and potential memory leak or instability when the specific driver path is exercised, for example when a process exits while the driver is trying to unmap CSA and free GPU VM structures. Multiple downstream trackers and distributions (Ubuntu, Debian, SUSE, Oracle Linux, NVD) document the same technical description and the stable‑tree commit that remedies the problem.

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What Microsoft actually said — and how to read it​

Microsoft’s Security Response Center entry for CVE‑2025‑38011 says, in plain language, that “Azure Linux includes this open‑source library and is therefore potentially affected” and notes that Microsoft began publishing CSAF/VEX machine‑readable attestations starting with Azure Linux; the company also pledges to update the CVE record if additional Microsoft products are discovered to ship the same upstream component. That phrasing is intentionally narrow and procedural:

• It is an attestation for the Azure Linux product family — Microsoft has completed an inventory for that product and found the implicated upstream component in those images.
• It is not an explicit claim that no other Microsoft product includes the same library. Absence of a VEX/CSAF entry for another Microsoft product is absence of attestation, not proof of absence.

Put simply: Microsoft has told customers which of its published product families it has checked and mapped to this CVE (Azure Linux). The company will expand that machine‑readable mapping if more Microsoft artifacts are later found to ship the vulnerable component. Customers should treat the Azure Linux attestation as authoritative for Azure Linux images, while performing artifact‑level verification for other Microsoft‑distributed kernels or images in their environment.

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Technical anatomy — why this matters​

The vulnerable code lives in the AMD GPU DRM driver stack. The reported failure mode happens during the CSA unmap and GPU VM free sequence: if a process exits, accepts a signal, and the thread waiting to take the VM lock is interrupted and returns, kernel data structures may be left in an inconsistent state leading to memory leaks and warning backtraces. The upstream fix switches the wait to an uninterruptible mode so the cleanup sequence cannot be prematurely interrupted by signals. Key technical points:

• The vulnerability is purely in kernel driver code (drm/amdgpu). Whether a system is vulnerable depends on whether the running kernel image contains that driver codepath and whether the kernel includes the upstream fix or vendor backport.
• Attack vector: local. An attacker or misbehaving process that can exercise DRM/amdgpu paths (for example, a compositor, an unprivileged process with /dev/dri access, or a container/VM with device passthrough) can provoke the condition. This is a denial‑of‑service/robustness risk rather than a remote RCE.

Because the vulnerability is contingent on kernel build configuration and the presence of the relevant module/code, you cannot determine exposure from a vendor statement alone — you must verify binaries and configurations on each artifact.

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Is Azure Linux the only Microsoft product that includes this library and is potentially affected?​

Short answer: No — Azure Linux is the only Microsoft product Microsoft has publicly attested (so far) as including the implicated upstream component for CVE‑2025‑38011, but that is not a proof that no other Microsoft product could include the same code.
Why that distinction matters:

• Microsoft’s VEX/CSAF output is a machine‑readable inventory mapping that says which Microsoft product artifacts have been inspected and what their status is. The fact that Azure Linux is listed means Microsoft verified it for Azure Linux; it does not mean the company inspected every other kernel image or Linux‑based product yet.
• Microsoft maintains multiple Linux kernel artifacts — for instance, the WSL2 kernel sources are public and include the drivers/gpu/drm tree where the amdgpu driver lives. Whether those kernels are built with amdgpu enabled, or whether a particular marketplace image or appliance ships a kernel with the vulnerable path, is an artifact‑level question that requires inspection.

In operational terms: treat Microsoft’s attestation as authoritative for Azure Linux only. For all other Microsoft artifacts (WSL, onboard kernels in Marketplace images, AKS node images, linux‑azure packages, and any Microsoft‑supplied VM/marketplace appliances), you must verify presence of amdgpu and kernel version / backports yourself, or wait for Microsoft to expand its VEX/CSAF inventory.

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Evidence and independent confirmation​

The technical description and upstream fix are recorded by independent, authoritative trackers and distribution advisories. Examples include:

• NVD and related CVE trackers list the same description and the upstream commit metadata for CVE‑2025‑38011.
• Major distributions (Ubuntu, Debian, SUSE, Oracle Linux) published advisories mapping CVE‑2025‑38011 to fixed kernel package versions. These pages corroborate the vulnerability scope (drm/amdgpu) and the remediation approach (stable kernel commits / vendor backports).

These independent confirmations are important because Microsoft’s VEX/CSAF statement addresses the product‑scope question (Azure Linux) while the broader technical community confirms the kernel patch and the paths by which the vulnerability propagates into distributor kernels.

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Practical implications — where to check in your environment​

Because the vulnerable code is kernel resident, exposure is determined by the kernel that runs on the host or VM, not by userland packages. Prioritize inspection of the following Microsoft‑supplied artifacts and places where Microsoft’s kernel artifacts may appear:

• Azure Linux VM images (high priority — Microsoft attested these images).
• WSL2 instances (either Microsoft‑supplied WSL kernel or a custom kernel specified via .wslconfig). Microsoft publishes the WSL‑kernel source tree; if your WSL uses the Microsoft binary, check for updates.
• Azure Marketplace images and appliances that include a Linux kernel.
• AKS node images or GPU‑enabled VM node pools that depend on underlying VM images with kernels that may include amdgpu. Container images themselves do not contain kernel code — vulnerability is host kernel dependent.

Short, runnable triage checks you can run on a host (quick inventory):

1. Identify running kernel: uname -r.
2. Check if amdgpu is loaded: lsmod | grep amdgpu.
3. Inspect module files: ls -l /lib/modules/$(uname -r)/kernel/drivers/gpu/drm/amd.
4. Check kernel config for amdgpu: zcat /proc/config.gz | egrep 'CONFIG_DRM_AMDGPU|CONFIG_DRM' or grep -i CONFIG_DRM_AMDGPU /boot/config-$(uname -r).
5. Inspect DRM device nodes and permissions: ls -l /dev/dri/*. If device nodes are accessible to unprivileged users or to containers, exposure increases.

If you manage WSL across developer fleets, confirm whether Windows Update delivered an updated WSL kernel package or whether you are using a custom WSL kernel — adapt accordingly.

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Recommended mitigations and remediation prioritization​

Patching the kernel remains the authoritative remediation. The recommended operational priorities:

• High priority: Patch and reboot Azure Linux instances — Microsoft has attested those images and will provide the updates in the Azure Linux release pipeline. Use your normal patch automation or Azure Update Management to deploy updates.
• High priority: For any host that loads the amdgpu module and exposes /dev/dri to untrusted tenants (multi‑tenant CI runners, shared VDI hosts, GPU‑enabled Kubernetes nodes), schedule kernel updates immediately. If patching must wait, restrict access to GPU device nodes and avoid binding GPUs into untrusted containers.
• Medium priority: WSL instances — ensure the Microsoft‑supplied WSL kernel is updated via Windows Update, or rebuild custom WSL kernels with the upstream fix if you maintain custom kernels. Pay attention to developer fleets and CI agents where untrusted code may run.
• Compensating controls when patching is not immediately feasible:
  • Restrict /dev/dri access via udev rules and group memberships.
  • Remove /dev/dri device passthrough from untrusted containers or CI runners (don’t pass devices unless necessary).
  • Temporarily blacklist the amdgpu module if GPU acceleration is nonessential (note: this disables GPU acceleration).
• Validation after patching: Reboot into the patched kernel and exercise representative display/GPU workloads, modeset flows and any VM passthrough scenarios used in production. Search kernel logs for previous oops patterns to confirm the behavior does not reappear.

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Operational guidance for Microsoft customers​

• Treat Microsoft’s VEX/CSAF attestation as the canonical signal for Azure Linux images. Microsoft’s machine‑readable output is intended for automation and deterministic triage for those images. Azure Linux tenants should act quickly on the attestation.
• For other Microsoft artifacts (WSL2 kernels, linux‑azure kernels, Marketplace images, AKS node images, vendor appliance images) — assume potential exposure until you verify the artifact’s kernel build configuration, module presence, and patch level. The presence of the upstream driver in a source tree or in Microsoft’s public kernel repos shows a plausible carriage vector, but exposure must be determined per binary image.
• Maintain a prioritized inventory and triage pipeline: list Microsoft‑published images you run, check the kernel version and amdgpu presence, consult vendor/distro advisory pages to map to fixed package versions, then schedule updates. Use the commands listed earlier for rapid triage.

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Risk analysis — strengths and residual risks​

Strengths in Microsoft’s approach

• Microsoft’s adoption of machine‑readable CSAF/VEX attestations for Azure Linux is a positive transparency step: it gives customers an authoritative mapping they can automate into asset management and patch orchestration systems. That reduces ambiguity for Azure Linux customers and allows accelerated remediation.
• The underlying fix upstream is small and targeted; major distributions and trackers have quickly mapped the stable commit into vendor kernels and published fixed package versions. This means remediation paths are available for most managed environments.

Residual and operational risks

• Artifact variance: Microsoft and many vendors ship multiple kernel artifacts with different build configs. A Microsoft product that is not yet listed in VEX/CSAF may still include the vulnerable code if its kernel build enabled the AMDGPU driver. Absence of attestation does not equal absence of code.
• Long‑tail devices and images: Embedded appliances, vendor images and marketplace appliances often lag upstream and may not receive timely backports. These long‑tail carriers remain an operational exposure until verified and patched.
• Local attack surface: Although the vector is local, many operational environments (shared CI, multi‑tenant GPU hosts, VDI) allow untrusted code to reach device nodes, increasing the practical risk of a targeted DoS.

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When Microsoft expands the VEX/CSAF mapping​

Microsoft has publicly committed to update CVE entries and its VEX/CSAF attestations if additional Microsoft products are identified as shipping the implicated open‑source component. That means the authoritative product mapping may grow over time as Microsoft completes inventory work across more product families. Organizations should monitor MSRC and subscribe to machine‑readable feeds to capture future mappings as they appear. Until those attestations are expanded, operational teams should not rely on “not mentioned = safe” logic; instead, verify kernels and plan patching accordingly.

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Conclusion — a pragmatic checklist​

• Azure Linux customers: treat the MSRC attestation as authoritative and patch Azure Linux images now.
• All organizations running Microsoft‑supplied Linux artifacts: inventory the artifacts, check kernel versions and amdgpu/module presence, and patch or mitigate based on exposure.
• WSL maintainers and developer fleets: confirm WSL kernel versions and update or rebuild custom kernels with the upstream fix if necessary.
• Use the simple triage commands (uname -r, lsmod | grep amdgpu, inspect /lib/modules and /dev/dri, check kernel configs) to determine whether a given system is likely vulnerable.

Microsoft’s statement that “Azure Linux includes this open‑source library and is therefore potentially affected” is correct and helpful for Azure Linux customers, but it answers only one operational question: “Which Microsoft product family did Microsoft inventory and map to this CVE?” It does not, by itself, prove that no other Microsoft artifact is a carrier. Treat the attestation as the starting point for automated triage — and perform artifact‑level verification and patching across any Microsoft kernels or images you operate.

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For immediate triage, run the commands under “Practical implications” on representative hosts and prioritize patching for hosts that: (a) run Azure Linux images; (b) load the amdgpu module; or (c) expose /dev/dri to untrusted workloads.

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Source: MSRC Security Update Guide - Microsoft Security Response Center