CVE-2025-37892: Linux Kernel MTD INFTL Error Handling Flaw

CVE-2025-37892 Overview

CVE-2025-37892 is a Linux kernel vulnerability in the Inverse NAND Flash Translation Layer (INFTL) memory technology device (MTD) subsystem. The INFTL_findwriteunit() function in drivers/mtd/inftlcore.c does not check the return value of inftl_read_oob(). When the out-of-band (OOB) read fails, the function continues processing with potentially uninitialized data instead of setting the sector status to SECTOR_IGNORE and breaking from the loop. A reference implementation for the correct pattern exists in INFTL_deleteblock().

Critical Impact
A local, low-privileged attacker interacting with an INFTL-managed MTD device can trigger the unchecked failure path, leading to high-severity impact on confidentiality, integrity, and availability of the affected kernel.

Affected Products

Linux kernel (multiple stable branches through 6.15-rc1)
Debian Linux 11.0 (see Debian LTS Announcement)
Distributions shipping affected kernel versions with the INFTL MTD driver enabled

Discovery Timeline

2025-05-20 - CVE-2025-37892 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-37892

Vulnerability Analysis

The vulnerability resides in the INFTL driver, which implements the Inverse NAND Flash Translation Layer used to abstract raw NAND flash devices for the MTD subsystem. Inside INFTL_findwriteunit(), the driver iterates over erase units searching for a writable location. During this iteration it calls inftl_read_oob() to retrieve OOB metadata that determines block status.

The original code does not check the return value of inftl_read_oob(). If the OOB read fails due to hardware error or corrupted flash, the caller proceeds as if the read succeeded and consumes stale or uninitialized status bytes. This leads to incorrect control flow inside the while-loop, potential kernel memory corruption, and undefined behavior in the flash translation layer.

Root Cause

The root cause is missing error handling on a function return value in kernel code. INFTL_deleteblock() already demonstrates the correct pattern: on failure, the block status is set to SECTOR_IGNORE, which forces the loop to exit cleanly. INFTL_findwriteunit() omitted this defensive check, leaving the algorithm operating on unchecked OOB data. NVD classifies this under [NVD-CWE-noinfo] pending further categorization.

Attack Vector

Exploitation requires local access with low privileges on a system that mounts or accesses an INFTL-managed MTD device. No user interaction is needed. An attacker who can influence the underlying flash content or induce OOB read failures, for example through a crafted or degraded flash image attached to a virtual or physical device, can drive INFTL_findwriteunit() into the unchecked failure path. The resulting kernel state can affect confidentiality, integrity, and availability of the host.

No verified public proof-of-concept code is available. The vulnerability is described in kernel commit messages linked from the kernel.org stable tree.

Detection Methods for CVE-2025-37892

Indicators of Compromise

Kernel log entries from the mtd or inftl subsystem reporting OOB read failures followed by anomalous block status changes.
Unexpected kernel oops, panic, or memory corruption warnings referencing INFTL_findwriteunit or inftl_read_oob in stack traces.
Filesystem corruption on INFTL-backed volumes without a preceding hardware error report.

Detection Strategies

Inventory hosts running kernels prior to the fix commits (1c22356, 5479a6a, 114d94f, e7d6cef, d027951, 6af3b92, 7772621, b828d39, 0300e75) and identify those with the INFTL driver compiled or loaded.
Monitor /proc/modules and boot logs for the presence of the inftl module on production systems where it is not required.
Correlate kernel ring buffer messages with process activity to identify local users triggering repeated MTD ioctl calls.

Monitoring Recommendations

Forward dmesg and /var/log/kern.log to a centralized logging platform and alert on MTD or INFTL errors.
Track loading of the inftl kernel module on endpoints and servers as a low-frequency, high-signal event.
Baseline expected MTD device usage per host and alert on unexpected access by non-privileged accounts.

How to Mitigate CVE-2025-37892

Immediate Actions Required

Apply the upstream Linux kernel patch from your distribution as soon as it is available. Debian users should follow the Debian LTS Announcement.
Restrict local access on multi-user systems and audit accounts with permissions to interact with /dev/mtd* devices.
If the INFTL driver is not required, unload the inftl module and blacklist it to eliminate the attack surface.

Patch Information

The fix adds an error check for inftl_read_oob() in INFTL_findwriteunit() and sets the sector status to SECTOR_IGNORE on failure so the while-loop terminates safely. The patch was merged across stable branches. Reference commits include 1c22356, 5479a6a, 114d94f, e7d6cef, d027951, 6af3b92, 7772621, b828d39, and 0300e75.

Workarounds

Blacklist the inftl kernel module on systems that do not use INFTL-managed NAND flash.
Tighten permissions on /dev/mtd* and /dev/mtdblock* device nodes so only trusted service accounts can access them.
Where feasible, migrate legacy INFTL flash volumes to supported filesystems and unload the driver.

bash

# Prevent the vulnerable INFTL module from loading
echo 'blacklist inftl' | sudo tee /etc/modprobe.d/blacklist-inftl.conf
echo 'install inftl /bin/true' | sudo tee -a /etc/modprobe.d/blacklist-inftl.conf

# Unload the module if currently loaded
sudo rmmod inftl 2>/dev/null || true

# Verify the module is not present
lsmod | grep inftl || echo "inftl module not loaded"