CVE-2025-39788 – A Linux kernel vulnerability in the UFS (Univer... (How to Fix)

Q: What is the severity of CVE-2025-39788?

CVE-2025-39788 has a CVSS score of 7.8 (HIGH). A Linux kernel vulnerability in the UFS (Universal Flash Storage) driver for Exynos chipsets allows undefined behavior due to integer overflow when programming hardware registers. This affects devices using Google gs101 chipsets with Linux kernel versions containing the buggy driver code. The vulnerability could potentially lead to system instability or privilege escalation.

📋 TL;DR

A Linux kernel vulnerability in the UFS (Universal Flash Storage) driver for Exynos chipsets allows undefined behavior due to integer overflow when programming hardware registers. This affects devices using Google gs101 chipsets with Linux kernel versions containing the buggy driver code. The vulnerability could potentially lead to system instability or privilege escalation.

💻 Affected Systems

Products:

Linux kernel with Exynos UFS driver

Versions: Kernel versions containing the vulnerable code (specific versions not specified in CVE)

Operating Systems: Linux

Default Config Vulnerable: ⚠️ Yes

Notes: Specifically affects systems with Google gs101 chipsets and 32 UTP transfer request slots (nutrs=32).

📦 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...

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

Kernel panic, system crash, or potential privilege escalation leading to full system compromise.

🟠

Likely Case

System instability, crashes, or undefined behavior in UFS storage operations.

🟢

If Mitigated

Minor performance impact or no noticeable effect if not triggered.

🌐 Internet-Facing: LOW - Requires local access to trigger the shift operation.

🏢 Internal Only: MEDIUM - Local users or processes could trigger the bug, potentially causing system instability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires triggering the specific shift operation with exact hardware configuration.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions with commit 01510a9e8222f11cce064410f3c2fcf0756c0a08 or later

Vendor Advisory: https://git.kernel.org/stable/c/01510a9e8222f11cce064410f3c2fcf0756c0a08

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commit. 2. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable UFS driver module

linux

Prevent loading of vulnerable ufs-exynos driver module

echo 'blacklist ufs-exynos' >> /etc/modprobe.d/blacklist-ufs-exynos.conf
rmmod ufs-exynos

🧯 If You Can't Patch

Restrict local user access to systems with vulnerable configuration
Monitor system logs for UBSAN warnings related to shift-out-of-bounds

🔍 How to Verify

Check if Vulnerable:

Check if system uses gs101 chipset and has kernel version before fix commit: 'uname -r' and check kernel source for vulnerable code

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes commit 01510a9e8222f11cce064410f3c2fcf0756c0a08: 'git log --oneline | grep 01510a9e8222'

📡 Detection & Monitoring

Log Indicators:

UBSAN: shift-out-of-bounds warnings in kernel logs
System crashes or instability related to storage operations

SIEM Query:

source="kernel" AND "shift-out-of-bounds" AND "ufs-exynos"

📊 Metadata

CVE ID: CVE-2025-39788

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

CWE: CWE-787

EPSS Score: 0.01% exploit probability (1th percentile)

Published: September 11, 2025

Last Updated: January 16, 2026

🔗 References

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