CVE-2025-71137: Linux Kernel Shift-Out-of-Bounds Flaw

CVE-2025-71137 Overview

CVE-2025-71137 is a vulnerability in the Linux kernel affecting the octeontx2-pf network driver. The flaw occurs when the RX ring size (rx_pending) is not properly validated before use, allowing users to pass small or zero ring sizes via the ethtool -G command. This leads to UBSAN (Undefined Behavior Sanitizer) shift-out-of-bounds errors, which can cause system instability or undefined behavior.

Critical Impact
Improper input validation in the octeontx2-pf driver allows local users to trigger undefined behavior through manipulated ring size parameters, potentially causing system instability.

Affected Products

Linux kernel (octeontx2-pf network driver)
Systems using Marvell OcteonTX2 network processors
Multiple stable kernel versions (patches available across various kernel branches)

Discovery Timeline

2026-01-14 - CVE-2025-71137 published to NVD
2026-01-19 - Last updated in NVD database

Technical Details for CVE-2025-71137

Vulnerability Analysis

The vulnerability exists in the octeontx2-pf driver, which handles network packet processing for Marvell OcteonTX2 processors. When a user configures the RX ring size using the ethtool -G interface, the driver fails to validate that the provided rx_pending value meets minimum size requirements. If a user supplies a value that is too small or zero, subsequent operations that depend on this value—particularly bitwise shift operations—can produce undefined behavior.

Shift-out-of-bounds errors occur when a shift operation attempts to shift a value by a number of bits that exceeds the size of the type or when the shift amount is negative. In this case, the undersized ring configuration propagates through the driver code and triggers UBSAN sanitizer warnings, indicating potential memory corruption or system instability.

Root Cause

The root cause is missing input validation in the octeontx2-pf driver's ring configuration handler. The driver did not enforce a minimum permitted length for the RX ring size before using it in subsequent calculations. This allows user-controlled input from ethtool -G to pass directly into shift operations without bounds checking, leading to undefined behavior when invalid values are processed.

Attack Vector

The attack requires local access to the system with sufficient privileges to modify network interface settings using ethtool. An attacker with such access can trigger the vulnerability by setting an invalid (small or zero) RX ring size parameter using the ethtool -G <interface> rx <value> command.

The exploitation path involves:

Attacker gains local access to a system with the octeontx2-pf driver loaded
Attacker uses ethtool -G to set the RX ring size to zero or a value below the minimum threshold
The driver processes the invalid value without proper validation
Shift operations using this value trigger UBSAN errors and undefined behavior

This vulnerability is a local privilege issue and does not have a known remote exploitation vector. The impact is limited to denial of service through system instability rather than code execution.

Detection Methods for CVE-2025-71137

Indicators of Compromise

UBSAN error messages in kernel logs referencing octeontx2-pf driver and shift-out-of-bounds
Kernel warnings or oops messages related to the otx2_set_ringparam function
Unexpected network driver behavior or crashes following ethtool configuration changes
System dmesg output containing "UBSAN: shift-out-of-bounds" with octeontx2 stack traces

Detection Strategies

Monitor kernel logs (dmesg, /var/log/kern.log) for UBSAN sanitizer warnings related to shift operations
Audit ethtool command usage on systems with octeontx2-pf driver, particularly -G flag operations
Deploy kernel runtime detection tools to catch undefined behavior sanitizer events
Review system call logs for suspicious network interface configuration changes

Monitoring Recommendations

Enable UBSAN in kernel builds to detect shift-out-of-bounds errors proactively
Configure syslog alerting for kernel UBSAN messages to enable rapid response
Monitor network interface configuration changes through auditd rules for ethtool invocations
Implement baseline monitoring for octeontx2-pf driver behavior and performance metrics

How to Mitigate CVE-2025-71137

Immediate Actions Required

Update the Linux kernel to a patched version that includes the boundary validation fix
Restrict ethtool access to trusted administrators only using appropriate permissions
Monitor systems for UBSAN errors in kernel logs indicating exploitation attempts
Consider temporarily restricting network interface configuration changes on affected systems

Patch Information

The Linux kernel maintainers have released multiple patches across stable kernel branches to address this vulnerability. The fix ensures that the RX ring size (rx_pending) is validated against a minimum permitted length before being used in driver operations.

Available kernel patches:

Workarounds

Restrict access to ethtool using filesystem permissions or SELinux/AppArmor policies
Disable or unload the octeontx2-pf driver if not required for system operation
Use kernel module parameters or driver configuration to enforce minimum ring sizes at load time
Apply network namespace isolation to limit interface configuration access

bash

# Restrict ethtool access to root only
chmod 750 /sbin/ethtool

# Verify current ring settings before applying updates
ethtool -g <interface>

# Monitor for UBSAN errors in kernel logs
dmesg | grep -i "UBSAN\|shift-out-of-bounds"