The Linux kernel fix for CVE-2025-37793 patches a straightforward but real null-pointer dereference in the Intel ASoC AVS driver: a missed NULL check on the return value of devm_kasprintf() inside avs_component_probe() can allow a failed allocation to lead directly to a kernel NULL-dereference and crash. This vulnerability is
local in scope and typically results in denial-of-service (kernel crash) rather than code execution, but it is meaningful for systems that ship the affected kernel drivers and load the AVS component.
Background / Overview
CVE-2025-37793 was assigned to a Linux kernel ASoC (ALSA System-on-Chip) driver issue in the Intel AVS component. Upstream maintainers fixed the problem by adding a defensive NULL check so that devm_kasprintf() failure no longer yields a dereferenced pointer during driver probe. The fix was merged into the stable kernel trees and is cataloged in the upstream patch commits referenced in public vulnerability databases. The vulnerability was first published on May 1, 2025, and vendors and distributions subsequently mapped, patched, and annotated the CVE across their advisories.
Technically the flaw is:
- Root cause: NULL return from devm_kasprintf() not checked inside avs_component_probe().
- Symptom: Kernel NULL-pointer dereference leading to an oops/panic and loss of availability.
- Attack vector: Local—an attacker or a misbehaving process that can trigger the AVS driver probe or related interfaces can provoke the crash.
- Severity: Medium (CVSS ~5.5 in public databases) because confidentiality/integrity impacts are low while availability impact can be high for affected hosts.
What Microsoft published — and what that wording actually means
Microsoft’s public advisory language for this and many Linux-kernel CVEs has followed the same pattern: a short, product-scoped attestation stating that
“Azure Linux includes this open‑source library and is therefore potentially affected.” That phrase is actionable for Azure Linux customers: it means Microsoft has inventory-checked the Azure Linux artifacts and found the upstream component implicated by the CVE. Microsoft also says it began publishing machine-readable CSAF/VEX attestations in October 2025 and will update CVE records if additional Microsoft products are identified as carriers.
However, it is important to parse what that sentence does
not say. The Microsoft statement is a
product-level attestation about the Azure Linux distribution that Microsoft maintains. It is not a categorical guarantee that no other Microsoft product or image contains the same upstream source file or compiled driver. In practical terms:
- If you run Azure Linux, treat Microsoft’s attestation as authoritative — your Azure Linux images are in scope and should be patched per Microsoft’s guidance.
- If you run other Microsoft-distributed artifacts (for example WSL2 kernel images, linux-azure kernel builds, Azure Marketplace images, AKS node images, or other Microsoft-supplied kernels), the absence of a public MSRC aSKUs does not prove they lack the affected AVS code. Microsoft has committed to expanding VEX/CSAF attestations as they complete artifact-level inventories; until then, the status of other artifacts is an operational unknown.
This product-scoped vs. exclusive-state distinction is the recurrent theme in Microsoft’s CVE entries for Linux components: the company confirms Azure Linux as a known carrier for the upstream code it inspected, and promises to update the mapping if other Microsoft product teams are found to ship the same component. Treat the MSRC mapping as accurate and actionable for Azure Linux, and conservatively treat other Microsoft artifacts as “not yet verified” until proven otherwise.
Cross-verification: what independent sources say
To avoid relying on a single source, we checked multiple independent databases and distribution advisories:
- The National Vulnerability Database (NVD) and OSV summarize the defect and link to the upstream kernel commits describing the patch and its intent. These records confirm the technical details of the NULL-check omission and the fix.
- Distribution trackers and vendor advisories (Ubuntu, Debian, Red Hat, AWS ALAS) include entries for CVE-2025-37793 and report patched statuses or package mappings. Those entries show the CVE was processed by mainstream Linux vendors and integrated into their vulnerability trackers.
- A consolidated CVE feed (CVEFeed/other vulnerability aggregators) lists kernel.org patch links and provides a CVSS assessment consistent with the distribution trackers.
These independent cross-checks corroborate the upstream fix, the moderate severity, and the fact that multiple Linux distributions tracked and responded to the CVE. That consistency strengthens confidence in the technical description and the practical remediation steps recommended below.
Who is truly at risk?
Short answer: any system that runs a kernel build which includes the Intel AVS driver (the ASoC avs component) in an affected revision is potentially at risk of a denial-of-service when the faulty probe path is exercised.
More concretely:
- Confirmed at-risk: Azure Linux images that Microsoft has inventory-checked and mapped to the CVE — Microsoft explicitly lists Azure Linux as a product that includes the implicated upstream library. Treat Azure Linux artifacts as in-scope and apply updates.
- Likely-but-unverified: **Other Microsoft-distSL2 kernels distributed by Microsoft, linux-azure kernel builds, Marketplace images and AKS node images could include the same upstream driver depending on their kernel configuration and the versions used in the build pipeline. Microsoft’s current public attestation does not automatically include those artifacts, but absence of attestation is not evidence of absence. Administrators should verify per-artifact.
- Other vendors: most mainstream Linux distributions have flagged or patched the CVE in their kernel packages; follow vendor patches and advisories (Ubuntu, Debian, Red Hat, etc.).
Risk is driven by three operational factors:
- Does the host ship a kernel that includes the AVS driver? (module present or built-in)
- Is that kernel version in the range that contains the flaw? (consult vendor CVE mappings)
- Can the AVS probe path be triggered by local activity or device enumeration on the host?
If the answer to all three is “yes,” the host should be considered in-scope for remedial action.
How to verify presence and scope quickly (practical steps for administrators)
Below are defensive, practical steps you can run on your systems to determine whether you are affected. Use these checks across Azure Linux instances and any Microsoft-distributed artifacts you operate.
- Identify your running kernel and kernel package
- Run: uname -a and capture kernel version and build string.
- Check installed kernel package via your package manager (rpm -q kernel / dpkg -l | grep linux-image).
- Check if the ASoC Intel AVS driver is present
- If the driver is a loadable module:
- Run: lsmod | grep avs or modinfo avs (or the exact module name used by the distribution).
- Search module files: find /lib/modules/$(uname -r) -type f -name 'avs' -print.
- If the driver is built into the kernel:
- Inspect kernel config: zcat /proc/config.gz | grep -i avs or check /boot/config-$(uname -r) for ASoC/AVS options.
- Inspect kernel sources or module strings for the vulnerable function name
- If you have kernel source packages installed, grep the tree for avs_component_probe or devm_kasprintf references.
- If a module exists, strings $(modinfo -n modulename) | xargs -I{} strings {} | grep -E "avs_component_probe|avs"
- Cross-check vendor advisory mapping
- Consult your distribution’s CVE tracker (Ubuntu, Debian, Red Hat) to confirm whether your kernel package is listed as vulnerable or fixed. For example, Ubuntu and other trackers list the CVE and its status per release.
- For Microsozure Linux
- WSL2: check the WSL2 kernel package or the runtime kernel shipped with your WSL installation. WSL kernels are custom-built; if the WSL kernel version is in the vulnerable range and includes the AVS driver, WSL hosts could be affected.
- Azure Marketplace / AKS images: use image inventories or image manifests to identify kernel versions and installed modules; treat unverified Microsoft images as “unknown” and patch or inspect them where possible.
These checks give you a quick, pragmatic inventory of whether a host actually contains the vulnerable code rather than relying only on vendor-level attestations.
Mitigation and remediation options
If you confirm the host includes the vulnerable AVS driver, prioritize remediation based on the host’s role and exposure.
- Preferred, permanent fix: Apply the vendor/kernel patch that contains the upstream commit(s). Reboot as required to run the updated kernel. Upstream patches were merged into the stable trees; distributions released package updates and CVE mappings. Consult your distro advisory for the fixed package version and apply through normal patch management pipelines.
- Short-term mitigation if immediate reboot/patching is not possible:
- If the AVS driver is a loadable module and your workload does not require it, unload and blacklist the module temporarily:
- sudo modprobe -r <avs_module_name>
- Add the module name to /etc/modprobe.d/blacklist.conf to prevent loading across reboots.
- Note: unloading may not be possible if the module is built-in or in use. Also, blacklisting can affect audio device availability; test before applying across production fleets.
- Isolation and containment:
- Limit local access to systems where the vulnerable driver would be useful to trigger. The attack vector is local; reducing the number of accounts that can load modules or trigger device enumeration reduces risk.
- Monitoring and detection:
- Deploy kernel crash detection and monitoring (e.g., collect oops/panic logs with persistent journald or kdump). Alert on OOPS patterns that might indicate attempts to trigger the probe path.
- Use host-based intrusion detection to detect local attempts to load drivers or interact with suspicious device nodes.
- Vendor playbook:
- If you run Azure Linux, apply Microsoft’s supplied updates or follow the MSRC advisory and the Azure Linux update channels. Microsoft’s attestation makes Azure Linux a clear first-priority to update.
How administrators should reason about Microsoft’s attestation (operational guidance)
Microsoft’se Linux is useful and authoritative for that product, but it is not an exclusivity certificate for all Microsoft artifacts. Operationally:
- Treat Azure Linux as known affected and patch it promptly. MSRC’s statement is explicit and actionable for those images.
- Treat other Microsoft artifacts (WSL kernels, linux-azure, Marketplace/AKS images) as unverified until Microsoft publishes additional VEX/CSAF attestations or until you perform artifact-level verification. Failure to do per-artifact checks could leave you exposed even if MSRC has not yet expanded the CVE mapping.
- Subscribe to MSRC’s machine-readable CSAF/VEX feeds to automate detection of future attestations — Microsoft began rolling those out in October 2025 and promised to expand mappings as inventories complete. Integrating VEX into your vulnerability management reduces manual triage overhead.
Risk analysis — strengths and potential gaps
Strengths
- The bug is local and not trivially exploitable remotely in standard configurations; the primary impact is denial-of-service via kernel crash rather than remote code execution.
- Upstream patching was quick and straightforward: maintainers added defensive checks and the fix was merged into stable trees, enabling vendors to incorporate the patch in regular updates.
- Major distributions tracked and processed the CVE in their advisory systems, giving administrators concrete package-level remediation steps.
Potential risks and gaps
- The attack vector is local: on multi-tenant hosts, ephemeral compute nodes, or developer machines where untrusted users have local access, denial-of-service is a practical risk.
- Microsoft’s public mapping covers Azure Linux but does not, by itself, certify that other Microsoft artifacts are unaffected. That gap requires administrators to perform artifact-level verification for Microsoft-supplied kernels outside Azure Linux. In cloud and hybrid environments, it is common to use multiple Microsoft-supplied kernel artifacts — the lack of a comprehensive vencreates operational friction and potential blind spots.
- Long-lived or sensitive nodes that cannot be patched immediately should be prioritized for mitigation, but temporary mitigations (unloading/blacklisting modules) may not be viable if the driver is built-in or required by the workload.
Recommended checklist for operators (prioritized)
- Patch Azure Linux images immediately using Microsoft’s guidance and your standard patch pipeline. Azure Linux is explicitly attested by Microsoft as potentially affected.
- Inventory kernel versions and module lists across your fleet and identify hosts with AVS driver present (see verification steps above).
- For other Microsoft-distributed artifacts (WSL2, linux-azure, Marketplace images, AKS nodes): treat them as unverified; perform artifact checks or request SBOM/VEX attestations from Microsoft for those SKUs.
- Apply vendor fixes for non-Microsoft distributions (Ubuntu, Debian, RHEL, Amazon Linux) where applicable; coordinate with distro-specific timelines.
- If immediate patching is impossible, consider unloading and blacklisting the AVS module on affected hosts (test first), and strengthen local access controls to prevent unprivileged users from triggering probe paths.
- Enable kernel crash monitoring and alerting so attempts or accidental triggers produce fast operational visibility.
- Integrate MSRC CSAF/VEX feeds into your vulnerability automation to detect when Microsoft expands product mappings; Microsoft began publishing VEX/CSAF in October 2025 and will update mappings when additional products are found to ship the vulnerable component.
Closing analysis — where certainty ends and caution begins
CVE-2025-37793 is a clear, fixable kernel robustness bug that was patched upstream and tracked by multiple distributions. For Azure Linux customers, Microsoft’s published attestation that “Azure Linux includes this open-source library and is therefore potentially affected” is an authoritative operational signal: patch Azure Linux artifacts.
Beyond Azure Linux, however, the statement should not be misread as a global guarantee about all Microsoft-distributed kernels and images. Microsoft’s current MSRC entries reflect a product-scoped inventory posture: Azure Linux has been checked and mapped; other Microsoft artifacts may or may not contain the same upstream driver depending on build choices and kernel configurations. Until Microsoft expands its VEX attestations or you independently verify artifact contents, treat other Microsoft-supplied kernels as
unknown and perform the verification steps listed above.
We verified the technical facts about the vulnerability against multiple authoritative sources — upstream kernel commits (referenced in OSV and vendor trackers), NVD/OSV summaries, and mainstream distro advisories — and cross-checked Microsoft’s attestation language as published in MSRC snapshots and local inventory commentary. This cross-referencing confirms the downstream remediation path and highlights the practical reasoning administrators must use when vendor attestations are product-scoped rather than global.
If you manage Azure Linux systems: patch now. If you run other Microsoft-supplied kernels: inventory, verify, and demand per-artifact attestations or perform the artifact inspection steps above. The Microsoft wording is accurate and helpful—but it is not a substitute for artifact-level verification when your attack surface includes multiple Microsoft-distributed kernel images.
Source: MSRC
Security Update Guide - Microsoft Security Response Center