CVE-2025-68819 Overview
A vulnerability has been identified in the Linux kernel's DVB-USB dtv5100 driver within the dtv5100_i2c_msg() function. The vulnerability arises from improper validation of user-controlled input, specifically the rlen (receive length) parameter. When this value is set larger than the allocated buffer size of st->data, an out-of-bounds memory access occurs, potentially leading to memory corruption, system instability, or exploitation for privilege escalation.
Critical Impact
User-controlled input can trigger out-of-bounds memory writes in the Linux kernel's DVB-USB dtv5100 driver, potentially allowing attackers to corrupt kernel memory or escalate privileges.
Affected Products
- Linux Kernel (DVB-USB subsystem with dtv5100 driver enabled)
- Systems with DTV5100 USB digital TV receivers
- Linux distributions with affected kernel versions
Discovery Timeline
- 2026-01-13 - CVE CVE-2025-68819 published to NVD
- 2026-01-13 - Last updated in NVD database
Technical Details for CVE-2025-68819
Vulnerability Analysis
The vulnerability exists in the dtv5100_i2c_msg() function within the DVB-USB dtv5100 driver. This driver handles I2C communication for DTV5100 USB digital television receivers. The function accepts an rlen parameter that specifies the length of data to be received, but fails to validate whether this value fits within the bounds of the destination buffer st->data.
When a user supplies an rlen value that exceeds the allocated size of st->data, the function proceeds to write data beyond the buffer boundaries. This out-of-bounds write can corrupt adjacent kernel memory structures, potentially leading to denial of service through kernel panics, or in more severe cases, could be leveraged for arbitrary code execution in kernel context.
The vulnerability is particularly concerning because the rlen value originates from user-controlled input, meaning a local attacker with access to the affected USB device interface could potentially exploit this flaw.
Root Cause
The root cause is a missing bounds check in the dtv5100_i2c_msg() function. The function trusts the user-supplied rlen parameter without verifying that it does not exceed sizeof(st->data). This violates the fundamental security principle of never trusting user input and represents a classic buffer overflow pattern where input length validation is absent.
Attack Vector
The attack requires local access to a system with a DTV5100 USB device or the ability to interact with the dtv5100 driver interface. An attacker would craft a malicious I2C message with an rlen value larger than the expected buffer size. When the driver processes this message, it writes beyond the allocated buffer, corrupting kernel memory. The attack flow involves:
- Attacker gains access to the DVB-USB device interface
- Attacker sends a crafted I2C message with an oversized rlen value
- The dtv5100_i2c_msg() function processes the message without bounds checking
- Data is written beyond the st->data buffer boundaries
- Kernel memory corruption occurs, potentially enabling privilege escalation
The vulnerability mechanism occurs in the I2C message handling path where the receive length parameter is used directly without validation. The fix involves adding proper range checking to ensure rlen does not exceed the allocated buffer size before proceeding with the data transfer operation. For technical implementation details, see the kernel git commit.
Detection Methods for CVE-2025-68819
Indicators of Compromise
- Unexpected kernel panics or oops messages related to the dtv5100 or DVB-USB subsystem
- Memory corruption warnings in kernel logs referencing I2C operations
- Unusual activity or access patterns on DVB-USB device interfaces
- System instability when DTV5100 USB devices are connected
Detection Strategies
- Monitor kernel logs for out-of-bounds access warnings using KASAN (Kernel Address Sanitizer) if enabled
- Deploy kernel live patching solutions to detect and prevent exploitation attempts
- Use SentinelOne Singularity platform to monitor for anomalous kernel behavior and memory access patterns
- Implement file integrity monitoring on kernel modules to detect unauthorized modifications
Monitoring Recommendations
- Enable kernel auditing for device driver interactions, particularly USB subsystems
- Configure alerting for kernel oops or panic events with stack traces mentioning dtv5100 or dvb-usb
- Monitor for unusual I2C message patterns or high-frequency device access
- Deploy endpoint detection and response (EDR) solutions capable of kernel-level visibility
How to Mitigate CVE-2025-68819
Immediate Actions Required
- Update the Linux kernel to a patched version that includes the bounds checking fix
- If updates are not immediately possible, consider disabling or blacklisting the dtv5100 module if not required
- Restrict physical access to USB ports on affected systems
- Review and limit user permissions for accessing USB device interfaces
Patch Information
The Linux kernel maintainers have released patches that add proper range checking to prevent the out-of-bounds vulnerability. Multiple kernel stable branches have received the fix. The patches are available through the following kernel git commits:
Workarounds
- Blacklist the dtv5100 module to prevent it from loading if the device is not required
- Restrict access to USB device nodes using udev rules to limit exposure
- Implement mandatory access control (MAC) policies using SELinux or AppArmor to restrict driver access
- Consider using hardware USB port blockers for systems where DVB-USB devices are not needed
# Configuration example
# Blacklist the dtv5100 module to prevent loading
echo "blacklist dtv5100" | sudo tee /etc/modprobe.d/blacklist-dtv5100.conf
# Unload the module if currently loaded
sudo modprobe -r dtv5100
# Verify the module is not loaded
lsmod | grep dtv5100
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
