CVE-2025-21690 – A vulnerability in the Linux kernel's storvsc S... (How to Fix)

Q: What is the severity of CVE-2025-21690?

CVE-2025-21690 has a CVSS score of 5.5 (MEDIUM). A vulnerability in the Linux kernel's storvsc SCSI driver allows hypervisor errors to trigger excessive warning logs, consuming CPU resources and causing denial of service within virtual machines. This affects Linux systems using Hyper-V virtualization with the storvsc driver. The issue is triggered by persistent hypervisor errors rather than direct external exploitation.

📋 TL;DR

A vulnerability in the Linux kernel's storvsc SCSI driver allows hypervisor errors to trigger excessive warning logs, consuming CPU resources and causing denial of service within virtual machines. This affects Linux systems using Hyper-V virtualization with the storvsc driver. The issue is triggered by persistent hypervisor errors rather than direct external exploitation.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions with vulnerable storvsc driver (specific versions not provided in CVE, but patches available for multiple stable branches)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems using Hyper-V virtualization with storvsc driver for SCSI storage. Requires hypervisor errors to trigger.

📦 What is this software?

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

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Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete VM unresponsiveness due to CPU exhaustion from log flooding, preventing troubleshooting and requiring VM restart from hypervisor level.

🟠

Likely Case

Performance degradation and potential service disruption within affected VMs when hypervisor storage errors occur.

🟢

If Mitigated

Minimal impact with ratelimited logs allowing continued VM operation and troubleshooting capability.

🌐 Internet-Facing: LOW - Requires hypervisor-level access or hypervisor errors, not directly exploitable from network.

🏢 Internal Only: MEDIUM - Could affect VM availability in Hyper-V environments during storage subsystem issues.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires hypervisor-level access to trigger persistent storage errors, making it more of a reliability issue than traditional security vulnerability.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel versions with commits: 01d1ebdab9ccb73c952e1666a8a80abd194dbc55, 088bde862f8d3d0fc52e40e66a0484a246837087, 182a4b7c731e95c08cb47f14b87a272b6ab2b2da, 81d4dd05c412ba04f9f6b85b718e6da833be290c, d0f0af1bafef33b3e2aa8c3a4ef44db48df9b0ea

Vendor Advisory: https://git.kernel.org/stable/c/

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Disable storvsc driver logging

linux

Reduce logging verbosity for storvsc driver to prevent log flooding

echo 'module storvsc +p' > /sys/kernel/debug/dynamic_debug/control

🧯 If You Can't Patch

Monitor hypervisor storage health to prevent persistent errors
Implement VM resource monitoring and alerting for CPU spikes from kernel logging

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if storvsc module is loaded: lsmod | grep storvsc && uname -r

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is patched and check git commit history for the fix commits

📡 Detection & Monitoring

Log Indicators:

Excessive 'storvsc' warning messages in kernel logs (dmesg)
High CPU usage by kernel logging processes

Network Indicators:

None - this is a local VM issue

SIEM Query:

source="kernel" AND "storvsc" AND ("warning" OR "error") | stats count by host

📊 Metadata

CVE ID: CVE-2025-21690

CVSS v3 Score: 5.5 (MEDIUM)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CWE: CWE-770

EPSS Score: 0.03% exploit probability (7.5th percentile)

Published: February 10, 2025

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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