CVE-2025-38403

7.8 HIGH

📋 TL;DR

This CVE addresses an uninitialized memory vulnerability in the Linux kernel's VMCI transport for vsock. Attackers could potentially read uninitialized kernel memory, leading to information disclosure or other security issues. Systems running affected Linux kernel versions with VMCI transport enabled are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not specified in CVE, but patches exist in stable kernel trees

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if VMCI transport for vsock is enabled and used (common in virtualization environments like VMware)

📦 What is this software?

Debian Linux by Debian

View all CVEs affecting Debian Linux →

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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⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel memory information disclosure leading to privilege escalation or system compromise through chained attacks

🟠

Likely Case

Information disclosure of kernel memory contents, potentially revealing sensitive data

🟢

If Mitigated

Minimal impact if VMCI transport is disabled or proper kernel hardening is in place

🌐 Internet-Facing: LOW - VMCI transport is typically used for local virtualization communication, not internet-facing services

🏢 Internal Only: MEDIUM - Could be exploited by local users or through virtualization environments

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access or ability to interact with VMCI transport; exploitation details not publicly available

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patches available in stable kernel trees (commits referenced in CVE)

Vendor Advisory: https://git.kernel.org/stable/c/0a01021317375b8d1895152f544421ce49299eb1

Restart Required: Yes

Instructions:

1. Update to patched kernel version from your distribution's repositories
2. Reboot system to load new kernel
3. Verify kernel version after reboot

🔧 Temporary Workarounds

Disable VMCI transport module

linux

Prevent loading of vmci_transport kernel module

echo 'blacklist vmci_transport' >> /etc/modprobe.d/blacklist-vmci.conf
rmmod vmci_transport

🧯 If You Can't Patch

Disable VMCI transport functionality if not required
Implement strict access controls to limit who can interact with vsock/VMCI interfaces

🔍 How to Verify

Check if Vulnerable:

Check if vmci_transport module is loaded: lsmod | grep vmci_transport

Check Version:

uname -r

Verify Fix Applied:

Check kernel version after update matches patched version from distribution

📡 Detection & Monitoring

Log Indicators:

Kernel logs showing vsock/VMCI errors or unusual activity

Network Indicators:

Unusual vsock communication patterns

SIEM Query:

process.name: 'kernel' AND (event.category: 'kernel' AND vsock OR vmci)

📊 Metadata

CVE ID: CVE-2025-38403

CVSS v3 Score: 7.8 (HIGH)

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

EPSS Score: 0.02% exploit probability (4.2th percentile)

Published: July 25, 2025

Last Updated: December 23, 2025

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Debian Linux by Debian

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

Linux Kernel by Linux

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable VMCI transport module

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export