Microsoft has publicly acknowledged that Azure Linux includes a vulnerable open-source component tied to CVE-2024-45026, a Linux kernel flaw in the s390 DASD driver that can lead to silent data corruption on thin-provisioned storage volumes. The advisory, published on Microsoft’s Security Response Center (MSRC) portal, immediately raises the question of whether other Microsoft products might also ship the same vulnerable code. For most Windows users, the direct risk is minimal, but Azure Linux customers and those managing IBM Z systems must act quickly.

What Changed: The Vulnerability and Microsoft’s Advisory

CVE-2024-45026 is a defect in the Linux kernel’s s390 DASD (Direct Access Storage Device) driver. The bug sits inside the dasdeseneedsformat function, which determines when a track on a thin-provisioned Extent Space Efficient (ESE) volume needs on-the-fly formatting. In certain error recovery scenarios—such as a storage server warmstart—the code misinterpreted transport errors as a missing format, causing write operations that could corrupt existing data rather than failing safely.

Upstream maintainers patched the kernel to check explicitly for invalid track formats and to remove an incorrect “file protected” check that did not apply to ESE handling. Because the flaw exists only in the s390 architecture code path, systems running on x8664 or ARM64 processors are not directly affected by this particular driver bug.

Microsoft’s MSRC advisory for CVE-2024-45026 includes the statement: “Azure Linux includes this open‑source library and is therefore potentially affected by this vulnerability.” The advisory does not claim that Azure Linux is the sole Microsoft product carrying the vulnerable component. Instead, it reflects a product-level inventory check—Microsoft has verified that Azure Linux kernels ship the upstream DASD driver code and are therefore in scope.

As the advisory explains, Microsoft began publishing CSAF/VEX (Common Security Advisory Framework / Vulnerability Exploitability eXchange) attestations in October 2025 to give customers machine-readable transparency into which products contain which open-source libraries. If Microsoft identifies additional products that include the vulnerable code, it will update the CVE entry accordingly.

What It Means for Your Systems

Azure Linux Customers: High Priority

If you run Azure Linux virtual machines, containers, or any Marketplace images derived from Azure Linux, Microsoft has confirmed you are potentially affected. The vulnerability can lead to silent data corruption on thin-provisioned ESE volumes attached to s390 hosts—a scenario most common on IBM Z mainframe systems. However, even if you are not running on s390 hardware today, the kernel code is present in Azure Linux builds; applying patches prevents future risk if you migrate or replicate images.

Action: Apply the latest Azure Linux updates immediately. Microsoft ships kernel fixes through its standard package channels. Consult the MSRC advisory for specific fixed kernel versions and package numbers.

Windows Desktop and Server Users: Low Direct Risk

Native Windows workloads—Windows 10, Windows 11, Windows Server—are not affected by this Linux kernel bug. The DASD driver is specific to the Linux kernel’s s390 architecture support; Windows does not use it. The risk is negligible for users who do not run Linux on their systems.

Exception: If you use Windows Subsystem for Linux 2 (WSL2) with custom kernels or if you have enabled WSL2 distributions that include s390 kernel components, you should verify. Official Microsoft WSL2 kernels are built for x8664 and ARM64, so DASD drivers are not compiled in by default. Run the detection commands in the remediation section to confirm.

IT Administrators in Hybrid Environments

Many organizations run a mix of Azure Linux VMs, on-premises Linux servers, and appliances. Because the vulnerable code is part of the upstream Linux kernel, any Microsoft-distributed Linux artifact that includes an s390 kernel build could carry the flaw. This includes:

  • Azure Marketplace images based on Azure Linux
  • Custom virtual appliances built from Azure Linux
  • WSL2 kernel source packages if s390 targets are compiled
  • Legacy or internal Microsoft kernel packages for specialized hardware

Use your software composition analysis (SCA) tools or SBOM scanners to inventory these artifacts. Even if you do not run s390 systems, the presence of the vulnerable code in your repositories is a compliance and supply chain concern.

IBM Z / s390 Mainframe Shops

If you operate IBM Z systems running Linux—especially Microsoft-provided images or kernels—this vulnerability is critical. Data corruption during error recovery on ESE volumes can be silent and irreversible. Apply patches immediately and run integrity checks on affected storage volumes after updating.

How We Got Here: A Deep Dive into the Kernel Bug and Microsoft’s Transparency Push

The s390 DASD driver is a niche but vital component for IBM Z mainframes, which rely on it to manage direct access storage. Extent Space Efficient (ESE) volumes are a form of thin provisioning that conserves disk space by allocating tracks only when data is written. The kernel must format these tracks on demand during normal I/O, and the dasdeseneedsformat function is responsible for deciding when formatting is necessary.

The flaw emerged from overly broad error checks. When a transport error occurred—such as a truncated packet during a storage server warmstart—the “incorrect length” flag was set, but the code lacked precise validation to distinguish between a genuine need for formatting and other transport failures. As a result, the driver could proceed with a write operation that assumed the track was unformatted, overwriting existing data.

Upstream Linux maintainers fixed the issue by refining the checks and removing the irrelevant “file protected” condition. The patch is straightforward but critical for data integrity.

Microsoft’s public advisory arrived as part of a broader initiative to improve supply chain transparency. In October 2025, the company began publishing CSAF/VEX documents, which provide machine-readable statements about whether a product is affected by a given vulnerability. The Azure Linux attestation for CVE-2024-45026 is one of the early results of this effort. By declaring Azure Linux as potentially affected, Microsoft gives security teams an authoritative starting point for remediation—but not a comprehensive map of every product line.

The distinction matters because kernel code is shared across many artifacts. A distribution like Azure Linux bundles the upstream kernel; other Microsoft products may incorporate the same kernel version or backported patches. Until Microsoft completes a cross-product inventory and publishes additional VEX statements, the absence of an attestation for other products does not guarantee they are free of the vulnerability. It simply means they have not been formally checked and acknowledged yet.

What to Do Now: A Practical Remediation Checklist

Step 1: Patch Azure Linux Immediately

  • Identify all Azure Linux instances in your environment (VMs, containers, Marketplace images).
  • Apply the latest kernel updates from Microsoft’s package repositories. Consult the MSRC advisory or your distribution’s update guide for specific kernel version numbers.
  • Rebuild any custom images derived from Azure Linux after patching.

Step 2: Inventory Other Microsoft Linux Artifacts

  • Use your asset management or SCA tools to locate Microsoft-supplied Linux images, kernels, or packages.
  • Pay special attention to artifacts flagged as multi-architecture or those that include s390x targets.
  • Extract SBOMs (software bills of materials) from container images and virtual appliances to check for the affected kernel component.

Step 3: Detect DASD Driver Presence

On any Linux system you suspect might be affected, run these commands to check for the vulnerable driver:

# Confirm architecture (look for s390x)
uname -m

Check if DASD kernel module is present

modinfo dasd lsmod | grep dasd

Search for DASD references in installed packages

rpm -qa | grep dasd # on RHEL/CentOS/Azure Linux dpkg -l | grep dasd # on Debian/Ubuntu

Inspect kernel version

uname -r

If the system is not s390x architecture and the DASD module is not loaded, the risk of exploitation via this specific CVE is extremely low. However, if you discover DASD drivers on any system, proceed to patch.

Step 4: Patch Non-Azure Linux Systems

  • If you run other Linux distributions that include the upstream s390 kernel code, apply the vendor’s security updates as soon as they are released.
  • For custom or embedded kernels, apply the upstream kernel patch or backport the fix. Verify that the dasdeseneeds_format function matches the corrected version by checking your source tree.

Step 5: Protect Data and Validate Fixes

  • For systems using ESE DASD volumes, create fresh backups and snapshots before applying patches.
  • After patching, run integrity checks on critical volumes. If you suspect corruption, consult your storage vendor’s recovery procedures.
  • Test patched systems in staging environments to ensure no regressions in regular I/O operations.

Step 6: Monitor Microsoft VEX/CSAF Updates

  • Bookmark the MSRC advisory page for CVE-2024-45026. Microsoft will update the listing if other products are confirmed as carriers.
  • Subscribe to security mailing lists or use automated tools that ingest CSAF/VEX feeds to stay informed about new attestations.

Outlook: The Bigger Picture for Supply Chain Security

CVE-2024-45026 is a niche vulnerability in practice, but the way Microsoft handled its disclosure illuminates a maturing approach to open-source supply chain transparency. The move to machine-readable VEX statements gives defenders a clearer signal than traditional advisory language—but it also requires them to understand the scope of those statements. An attestation that “Azure Linux is potentially affected” is a call to action for Azure Linux users, not a definitive boundary for the entire product portfolio.

Going forward, enterprise security teams should demand SBOMs from all software vendors and pair vendor attestations with their own automated scanning. This vulnerability also serves as a reminder that architecture-specific kernel bugs can lurk unnoticed in multi-arch distributions, making regular component inventories essential. As Microsoft expands its CSAF/VEX coverage, expect faster identification and remediation of shared open-source flaws—but until then, a trust-but-verify approach rooted in runtime detection and source-level checks remains the safest path.