Microsoft’s July 2025 advisory for CVE-2025-38425 confirms that Azure Linux kernels are vulnerable to a local out-of-bounds read bug. For the first time, the company is delivering that news in a machine-readable attestation format. But the new transparency spotlights a blind spot: Microsoft hasn’t yet attested whether its many other Linux-based offerings—from WSL2 kernels to AKS node images—contain the same flawed code. Customers must do their own inventory.

What CVE-2025-38425 Is, and How Microsoft Is Communicating It

CVE-2025-38425 is a flaw in the Linux kernel’s I2C subsystem, specifically in the Tegra driver’s SMBUS block-read handling. When a device reports a length of 0 or a number larger than the permitted maximum, the kernel could perform an out-of-bounds read, potentially causing instability or data leaks. The upstream fix—committed earlier this year—adds two simple checks that abort the read before any damage can occur.

The vulnerability landed on public trackers in July 2025. Microsoft’s Security Response Center (MSRC) issued its own advisory shortly after, but the notable change is the way the information is presented. Since October 2025, Microsoft has been publishing machine-readable CSAF/VEX documents for vulnerabilities, giving security teams an automatable way to see which products are affected. For CVE-2025-38425, the advisory states plainly: “Azure Linux includes this open-source library and is therefore potentially affected.”

That sentence is authoritative for Azure Linux—it means Microsoft has completed its inventory of that product line and knows the vulnerable code is present. The advisory also promises that if other products are later found to include the library, Microsoft will update the CVE record.

What This Means for Azure Linux Customers

If you run Azure Linux images in the cloud or on-premises, this advisory is your red flag. Microsoft has done the inventory work for you. You don’t need to guess whether the Tegra I2C driver is compiled into your kernel; it is. Your next step is clear: patch immediately.

Azure Linux updates that carry the fixed kernel are already available through the normal package channels. Apply them, reboot, and you’re done. Because Microsoft has attested the product is affected, you can also feed the machine-readable VEX data into your vulnerability management pipeline. Tools that consume CSAF can automatically flag every Azure Linux instance as vulnerable and trigger remediation workflows. That’s a big step forward from the old days of manually reading plain-text advisories.

What This Means If You Run Other Microsoft-Supplied Linux Kernels

Here’s where the confusion starts. Microsoft ships Linux kernels in many forms beyond the official Azure Linux distro:

  • WSL2 kernels – the default kernel that powers Windows Subsystem for Linux 2, plus any custom kernels organizations build for WSL.
  • linux-azure kernels – certain Azure virtual machine SKUs use a Microsoft-tuned kernel that isn’t the same as the Azure Linux distro.
  • Azure Marketplace images – virtual machine images from Microsoft and partners that may include their own kernel builds.
  • AKS node images – the kernel used by Azure Kubernetes Service worker nodes.
  • Appliance images – embedded kernels in Azure Stack Edge or other integrated systems.

None of these products are mentioned in the CVE-2025-38425 advisory. That doesn’t mean they’re safe. Microsoft’s advisory explicitly covers only what has been inventoried so far. For everything else, silence is not a “not affected” statement; it’s “not yet verified.”

The Tegra I2C driver is niche—it targets NVIDIA Tegra hardware, not x86 servers. But kernel configuration varies widely between builds. A linux-azure kernel packaged for an ARM64 VM, or a custom WSL kernel with broad hardware support, could easily include the driver as a module. Until Microsoft publishes a VEX attestation for each product, the only sane assumption is “unknown.”

How We Got Here: Microsoft’s VEX Rollout

In October 2025, Microsoft announced it would start publishing vulnerability exploitability eXchange (VEX) documents as part of the Common Security Advisory Framework (CSAF). The goal was to give customers automated, product-scoped signals instead of the vague, catch-all advisories of the past. That rollout is phased—Microsoft is working through its massive product catalog, attesting one family at a time.

CVE-2025-38425 is one of the first opportunities to see the approach in action. For Azure Linux, it’s a win: a single, deterministic record tells you exactly what’s affected. But the same mechanism reveals the accountability gap. Because attestations are product-by-product, they don’t cover all code paths Microsoft ships. The burden of discovering whether a linux-azure kernel or a Marketplace VM image contains the bug falls squarely on the operator.

This isn’t unique to Microsoft. Any large vendor wrestling with upstream open-source components faces the same challenge. The difference now is transparency: Microsoft is saying, “Here’s what we know for sure; for the rest, we’re working on it.” That honesty is useful, but it demands extra caution from security teams.

What to Do Now: Verification and Remediation Steps

1. Patch Azure Linux immediately

If you run any Azure Linux instance, stop reading and apply the latest kernel update. Check your distribution’s security tracker for the specific package version, or simply run your usual update command. For example:

sudo apt update && sudo apt upgrade   # Debian/Ubuntu-based Azure Linux
sudo dnf update kernel                # RPM-based Azure Linux

Reboot to load the new kernel. Confirm the CVE is addressed by checking the changelog: 

apt changelog linux-image-$(uname -r) | grep -i 38425
dnf changelog kernel | grep -i 38425

2. Inventory every other Microsoft-supplied kernel artifact

Make a list of all places you might be getting a kernel from Microsoft:

  • Your WSL installations (wsl --list --verbose)
  • Azure VMs using specialized kernel SKUs (check the VM configuration for “linux-azure”)
  • Any custom Marketplace images or AKS clusters
  • Appliances that run Microsoft-provided Linux

For each artifact, you need to answer one question: is the Tegra I2C driver present and vulnerable? Use these checks on running systems:

Check if the driver module exists:

lsmod | grep -i tegra
grep -r "tegra" /lib/modules/$(uname -r)/kernel

Inspect the kernel config for I2C Tegra support:

zgrep CONFIG_I2C_TEGRA /proc/config.gz
grep CONFIG_I2C_TEGRA /boot/config-$(uname -r)

Look for the CVE in the kernel’s changelog (distro-dependent):

apt changelog linux-image-$(uname -r) | grep -i 38425   # Debian/Ubuntu
rpm -q --changelog kernel | grep -i 38425               # RPM-based
yum --changelog kernel | grep -i 38425                  # Older RHEL

For offline images, mount the file system and inspect the kernel config or search for module files under /lib/modules/. Software composition analysis tools that consume SBOMs can also detect the presence of the vulnerable upstream source file across your entire estate.

If the driver is present and the kernel version predates the fix, treat the system as vulnerable.

3. Apply patches or workarounds

For each affected artifact, apply the vendor-provided kernel update through your normal channel. If the artifact comes from a Microsoft pipeline (e.g., a linux-azure kernel), you may need to wait for Microsoft to release an updated version. Subscribe to the MSRC feed for CVE-2025-38425 to get notified when attestations expand.

While waiting for a patch, you can apply mitigating controls:

  • Blacklist the Tegra I2C module to prevent it from loading:
    bash echo "blacklist i2c_tegra" | sudo tee /etc/modprobe.d/blacklist-tegra.conf sudo update-initramfs -u # Debian/Ubuntu sudo dracut -f # RHEL/CentOS
  • Restrict access to device nodes with udev rules.
  • Monitor kernel logs for any Tegra-related errors: journalctl -k | grep -i tegra.

4. Automate the process going forward

Integrate Microsoft’s CSAF/VEX feed into your vulnerability management platform. Tools like Trivy, Grype, or commercial scanners can ingest VEX documents and automatically suppress or flag findings based on official attestations. That will save you manual checks for future CVEs.

Outlook: More Attestations Ahead

Microsoft has committed to expanding its VEX coverage, and CVE-2025-38425 is a test case for the community. As the company finishes inventory for other product lines, it will update the advisory with new attestations. That means the list of “known affected” products could grow.

Until then, the lesson is clear: vendor attestations are a powerful tool, but they are a floor, not a ceiling. For Azure Linux, the advisory closes the loop. For everything else, your own verification is the only safety net. The drive toward machine-readable transparency is a win for defenders—as long as we remember that an advisory for one product never absolves us of checking the rest.