CVE-2024-50290: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-50290 Overview

CVE-2024-50290 is an integer underflow vulnerability in the Linux kernel's cx24116 DVB-S demodulator driver. The flaw resides in the Signal-to-Noise Ratio (SNR) calculation logic within the media subsystem. When SNR register reads fail, the driver returns a negative value that propagates into subsequent arithmetic, producing an underflow condition [CWE-191].

Coverity static analysis identified the issue, which the Linux kernel maintainers resolved upstream. The vulnerability affects multiple stable kernel branches and 6.12 release candidates rc1 through rc6.

Critical Impact
A local authenticated user interacting with the cx24116 DVB driver can trigger an integer underflow during SNR register read failures, leading to kernel-level availability impact.

Affected Products

Linux Kernel (multiple stable branches prior to fix commits)
Linux Kernel 6.12-rc1 through 6.12-rc6
Debian Linux distributions consuming affected kernels

Discovery Timeline

2024-11-19 - CVE-2024-50290 published to NVD
2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-50290

Vulnerability Analysis

The cx24116 driver supports Conexant CX24116-based DVB-S satellite tuner hardware in the Linux kernel media subsystem. The driver exposes SNR statistics through standard DVB ioctl interfaces. During SNR computation, the driver reads values from hardware registers over the I2C bus.

When a register read operation fails, the helper function returns a negative error code instead of a valid register value. The original code path did not validate this return value before using it in arithmetic operations. The negative value then participates in unsigned arithmetic or shift operations, producing an underflow.

The issue is classified as an integer underflow weakness [CWE-191]. Exploitation requires local access and low privileges, but no user interaction. The impact is constrained to availability — confidentiality and integrity remain unaffected.

Root Cause

The root cause is missing return-value validation in the cx24116 SNR calculation routine. Functions that read DVB hardware registers can return negative errno values when I2C transactions fail. The driver treated these signed error returns as if they were valid unsigned register contents. The patched code explicitly checks for read failure and aborts the calculation before any arithmetic occurs.

Attack Vector

Exploitation requires a local user with permission to open the /dev/dvb/adapterX/frontendX device node and issue FE_READ_SNR ioctl calls against affected cx24116 hardware. By inducing I2C read failures — through hardware manipulation, driver state corruption, or repeated stress on the bus — an attacker can force the underflow path. The resulting kernel-side computation error can produce a denial-of-service condition on the DVB subsystem.

The vulnerability is not remotely reachable. No public proof-of-concept exploit is available, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2024-50290

Indicators of Compromise

Unexpected kernel log entries referencing cx24116 I2C read errors or DVB frontend errors
Repeated FE_READ_SNR ioctl calls from unprivileged or unexpected processes against /dev/dvb/adapter*/frontend*
Kernel taint or warning messages emitted from the cx24116 module during SNR queries

Detection Strategies

Inventory running kernel versions across Linux hosts and compare against the fixed commits in git.kernel.org stable branches
Monitor for processes that open DVB frontend device nodes when no legitimate broadcast-reception workload is expected
Audit loaded kernel modules and flag systems that have cx24116 loaded without an associated media application

Monitoring Recommendations

Collect dmesg and journald output centrally and alert on cx24116 or dvb-frontend error patterns
Track ioctl activity on /dev/dvb/* device nodes via auditd rules
Correlate kernel-module load events with the user context that triggered them to identify anomalous access

How to Mitigate CVE-2024-50290

Immediate Actions Required

Apply the latest stable kernel update from your distribution that includes the upstream fix commits
For Debian systems, install kernel updates referenced in the Debian LTS Announcement (January 2025) and Debian LTS Announcement (March 2025)
Restrict access to /dev/dvb/* device nodes to trusted users and groups only
Blacklist the cx24116 module on systems that do not require DVB-S tuner support

Patch Information

The fix is distributed across multiple stable kernel branches. Reference commits include 127b9076bae, 3a1ed994d94, 576a307a765, 828047c70f4, 83c152b55d8, cad97ca8cfd, f2b4f277c41, and fbefe31e459. The patches add return-value validation before SNR arithmetic.

Workarounds

Blacklist the cx24116 module via /etc/modprobe.d/blacklist-cx24116.conf on hosts without DVB-S hardware
Apply restrictive Unix permissions and ACLs on /dev/dvb/* to prevent unprivileged ioctl access
Use Linux Security Modules (SELinux or AppArmor) policies to confine processes that interact with DVB frontends

bash

# Blacklist the cx24116 module on systems without DVB-S hardware
echo "blacklist cx24116" | sudo tee /etc/modprobe.d/blacklist-cx24116.conf
sudo depmod -a
sudo update-initramfs -u

# Verify the module is not loaded
lsmod | grep cx24116