CVE-2025-38535

Q: What is the severity of CVE-2025-38535?

CVE-2025-38535 has a CVSS score of 7.8 (HIGH). This vulnerability in the Linux kernel's Tegra XUSB PHY driver causes unbalanced regulator disable operations when transitioning USB roles. It can trigger kernel warnings and potentially cause system instability or crashes. Affects systems using NVIDIA Tegra processors with the affected kernel driver.

7.8 HIGH

Denial of Service

📋 TL;DR

This vulnerability in the Linux kernel's Tegra XUSB PHY driver causes unbalanced regulator disable operations when transitioning USB roles. It can trigger kernel warnings and potentially cause system instability or crashes. Affects systems using NVIDIA Tegra processors with the affected kernel driver.

💻 Affected Systems

Products:

Linux kernel with Tegra XUSB PHY driver

Versions: Kernel versions containing the vulnerable code up to the fix commits

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with NVIDIA Tegra processors (particularly Tegra186/Tegra194) and when using UTMI PHY mode with USB role switching.

📦 What is this software?

Debian Linux by Debian

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⚠️ Risk & Real-World Impact

🔴

Worst Case

System crash or kernel panic due to regulator subsystem corruption, leading to denial of service and potential data loss.

🟠

Likely Case

Kernel warning messages in system logs and potential USB functionality issues, but unlikely to cause full system crashes in most configurations.

🟢

If Mitigated

Minor performance impact or warning messages if regulator is marked as always-on, but no security compromise.

🌐 Internet-Facing: LOW - This is a local driver issue requiring physical or local USB device interaction.

🏢 Internal Only: MEDIUM - Could affect embedded systems, IoT devices, or servers with Tegra hardware if USB devices are frequently connected/disconnected.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires physical USB device interaction or privileged access to trigger USB role transitions. No known remote exploitation vectors.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits 1bb85b5c2bd43b687c3d54eb6328917f90dd38fc and related fixes

Vendor Advisory: https://git.kernel.org/stable/c/1bb85b5c2bd43b687c3d54eb6328917f90dd38fc

Restart Required: Yes

Instructions:

1. Update to a kernel version containing the fix commits. 2. For embedded systems: Update the kernel through your board support package or vendor updates. 3. Reboot the system after kernel update.

🔧 Temporary Workarounds

Disable USB role switching

linux

Prevent USB role transitions that trigger the vulnerability

echo '0' > /sys/class/udc/*/soft_connect
modprobe -r tegra-xusb-padctl || true

Mark regulator as always-on

linux

Configure the regulator to stay enabled, avoiding disable attempts

Add 'regulator-always-on' property to the regulator node in device tree

🧯 If You Can't Patch

Avoid connecting/disconnecting USB devices that trigger role switching
Monitor system logs for WARNING messages about unbalanced regulator disables

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if Tegra XUSB driver is loaded: 'uname -r' and 'lsmod | grep tegra_xusb'

Check Version:

uname -r

Verify Fix Applied:

Check kernel version includes fix commits: 'git log --oneline | grep -E "1bb85b5c2bd43b687c3d54eb6328917f90dd38fc|5367cdeb75cb6c687ca468450bceb2602ab239d8"'

📡 Detection & Monitoring

Log Indicators:

WARNING messages about 'unbalanced disables for VIN_SYS_5V0' or '_regulator_disable' in kernel logs
dmesg | grep -i "unbalanced disables\|regulator_disable"

Network Indicators:

None - this is a local driver issue

SIEM Query:

source="kernel" AND "unbalanced disables" OR "_regulator_disable"

📊 Metadata

CVE ID: CVE-2025-38535

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: 0.01% exploit probability (2.3th percentile)

Published: August 16, 2025

Last Updated: January 7, 2026

🔗 References

https://git.kernel.org/stable/c/1bb85b5c2bd43b687c3d54eb6328917f90dd38fc Patch
https://git.kernel.org/stable/c/5367cdeb75cb6c687ca468450bceb2602ab239d8 Patch
https://git.kernel.org/stable/c/cdcb0ffd6448f6be898956913a42bd08e59fb2ae Patch
https://git.kernel.org/stable/c/ceb645ac6ce052609ee5c8f819a80e8881789b04 Patch
https://git.kernel.org/stable/c/cefc1caee9dd06c69e2d807edc5949b329f52b22 Patch
https://git.kernel.org/stable/c/eaa420339658615d26c1cc95cd6cf720b9aebfca Patch
https://git.kernel.org/stable/c/ec7f98ff05f0649af0adeb4808c7ba23d6111ef9 Patch
https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html Third Party Advisory,Mailing List
https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html Third Party Advisory,Mailing List

📋 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

Linux Kernel by Linux

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable USB role switching

Mark regulator as always-on

🧯 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

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