CVE-2024-50290: Linux Kernel SNR Overflow Vulnerability

CVE-2024-50290 Overview

CVE-2024-50290 is an Integer Underflow vulnerability in the Linux kernel's cx24116 DVB-S/S2 frontend driver. The vulnerability exists in the Signal-to-Noise Ratio (SNR) calculation routine, where failed register reads can return negative values. When these negative values are used in subsequent arithmetic operations, an integer underflow occurs, potentially leading to system instability or denial of service conditions.

The vulnerability was identified through static code analysis by Coverity, which flagged the improper handling of error return values in the SNR register reading functions. This issue affects systems using the cx24116 DVB tuner for satellite reception.

Critical Impact

Local attackers with access to systems using the cx24116 DVB driver can trigger integer underflows through manipulated hardware states or driver interactions, potentially causing kernel panics or system crashes.

Affected Products

• Linux Kernel versions prior to patched releases across multiple stable branches
• Linux Kernel 6.12 Release Candidates (rc1 through rc6)
• Systems with Conexant cx24116 DVB-S/S2 satellite tuner hardware

Discovery Timeline

• November 19, 2024 - CVE-2024-50290 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2024-50290

Vulnerability Analysis

This vulnerability resides in the cx24116 media driver, specifically within the code path responsible for calculating the Signal-to-Noise Ratio from hardware registers. The driver reads SNR values from the tuner's registers to provide signal quality information to userspace applications.

The fundamental issue is that register read operations can fail due to I2C communication errors, hardware malfunctions, or timing issues. When such failures occur, the read functions return negative error codes (such as -EAGAIN or -EIO). The original code did not properly validate the return values before using them in SNR calculations.

When a negative error code is interpreted as an unsigned value or used in arithmetic operations expecting positive values, an integer underflow occurs. This results in extremely large values that can corrupt data structures, cause buffer overflows in dependent code paths, or trigger assertion failures leading to kernel panics.

Root Cause

The root cause is improper validation of return values from register read operations in the cx24116 driver's SNR calculation routine. The code assumes successful reads without checking for error conditions, leading to CWE-191 (Integer Underflow) when negative error codes are processed as valid data values.

The fix involves adding proper error checking after register read operations to ensure that negative return values are handled gracefully rather than being passed to arithmetic operations that expect valid SNR data.

Attack Vector

The attack vector is local, requiring an attacker to have access to a system with the vulnerable cx24116 DVB hardware. Exploitation could occur through:

1. Triggering I2C bus errors through hardware manipulation or timing attacks
2. Exploiting race conditions during driver initialization or signal acquisition
3. Manipulating the hardware state to force register read failures
4. Using malicious userspace applications that rapidly query SNR information during error conditions

The vulnerability requires local access and low privileges to exploit, though no user interaction is required. The primary impact is availability (denial of service through system crashes), with no direct confidentiality or integrity impact.

Detection Methods for CVE-2024-50290

Indicators of Compromise

• Unexpected kernel panics or system crashes on systems with cx24116 DVB hardware
• Kernel log messages indicating integer overflow or underflow conditions in media subsystem
• Anomalous SNR values reported by DVB applications (extremely large values indicating underflow)
• I2C bus errors preceding system instability

Detection Strategies

• Monitor kernel logs for cx24116 driver errors or warnings using dmesg or journalctl
• Implement kernel crash dump analysis to identify integer underflow patterns in media drivers
• Use static analysis tools to scan for similar patterns in custom kernel modules
• Deploy runtime integrity monitoring to detect abnormal driver behavior

Monitoring Recommendations

• Enable kernel logging at debug level for media subsystem during troubleshooting
• Configure crash reporting to capture kernel panics for forensic analysis
• Monitor system stability metrics on servers with DVB hardware
• Implement SentinelOne Singularity platform for real-time kernel anomaly detection

How to Mitigate CVE-2024-50290

Immediate Actions Required

• Update Linux kernel to patched versions containing the fix
• If immediate patching is not possible, consider disabling or unloading the cx24116 module
• Review systems inventory for devices using Conexant cx24116 DVB hardware
• Apply distribution-specific security updates from Debian, Ubuntu, or your Linux distribution

Patch Information

Multiple patches have been released across various Linux kernel stable branches. The fixes add proper validation of register read return values to prevent integer underflows. Key commits include:

• Kernel Commit 127b9076baea
• Kernel Commit 3a1ed994d945
• Kernel Commit 576a307a7650
• Kernel Commit 828047c70f47
• Kernel Commit 83c152b55d88

Debian users should refer to the Debian LTS Security Announcements for distribution-specific updates.

Workarounds

• Unload the cx24116 kernel module if DVB-S/S2 functionality is not required: modprobe -r cx24116
• Blacklist the module by adding blacklist cx24116 to /etc/modprobe.d/blacklist.conf
• Restrict physical access to systems with vulnerable DVB hardware
• Monitor systems closely for signs of exploitation until patches can be applied

# Temporarily disable the vulnerable module
sudo modprobe -r cx24116

# Permanently blacklist the module (if DVB functionality not needed)
echo "blacklist cx24116" | sudo tee /etc/modprobe.d/blacklist-cx24116.conf
sudo update-initramfs -u