CVE-2025-68808: Linux Kernel Use-After-Free Vulnerability

CVE-2025-68808 Overview

A use-after-free and double-free vulnerability has been discovered in the Linux kernel's vidtv (Virtual Digital TV) driver. The vulnerability exists in the vidtv_channel_si_init() function, which creates temporary lists for program, service, and event data. When memory ownership is transferred to PAT/SDT/EIT tables through the vidtv_psi_pat_program_assign(), vidtv_psi_sdt_service_assign(), and vidtv_psi_eit_event_assign() functions, local pointers are not properly initialized to NULL after the transfer completes.

This improper memory management allows for a dangerous scenario where memory that has already been freed can be accessed and freed again, leading to use-after-free and double-free conditions that could result in system instability or potential privilege escalation.

Critical Impact

Local attackers with access to the vidtv subsystem could exploit this memory corruption vulnerability to cause kernel crashes or potentially execute arbitrary code with kernel privileges.

Affected Products

• Linux kernel (vidtv driver component)
• Systems utilizing Virtual Digital TV functionality
• Linux-based media servers and DVB implementations

Discovery Timeline

• 2026-01-13 - CVE CVE-2025-68808 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2025-68808

Vulnerability Analysis

The vulnerability resides in the vidtv subsystem of the Linux kernel, specifically within the Service Information (SI) initialization routines. The vidtv_channel_si_init() function is responsible for creating and managing temporary data structures for programs, services, and events that are fundamental to Digital Video Broadcasting (DVB) implementations.

During normal operation, memory ownership is transferred from local pointers to the PSI (Program Specific Information) tables through dedicated assignment functions. However, the implementation fails to set the local pointers to NULL after this ownership transfer is completed. When vidtv_psi_pmt_create_sec_for_each_pat_entry() subsequently fails, the error handling path (free_eit label) attempts to destroy the tables using vidtv_psi_*_table_destroy(). Because the local pointers still reference the already-freed memory, the cleanup routines vidtv_psi_*_event_destroy() are invoked on invalid memory addresses, triggering a double-free condition.

Root Cause

The root cause is a failure to follow proper memory ownership semantics in C programming. When memory ownership is transferred from one data structure to another, the original pointer should be set to NULL to prevent any subsequent accidental access or deallocation. The vidtv driver omitted this critical step, leaving dangling pointers that point to memory regions that have already been freed and potentially reallocated for other purposes.

Attack Vector

An attacker with local access to a system running the vulnerable vidtv driver could potentially trigger this vulnerability by manipulating the DVB subsystem to cause the PMT section creation to fail after memory ownership has been transferred but before the local pointers are cleared. This could be achieved through:

1. Crafting specific input that triggers the failure path in vidtv_psi_pmt_create_sec_for_each_pat_entry()
2. Resource exhaustion attacks that cause memory allocation failures at the critical point
3. Race conditions during SI initialization

The vulnerability manifests in the memory ownership transfer mechanism within the vidtv driver. When vidtv_channel_si_init() transfers ownership of program, service, and event structures to the PSI tables, the local pointers retain their original values. If an error occurs after this transfer but before successful completion, the error handling path frees memory twice - once through the table destroy functions and again through the local pointer cleanup. For technical implementation details, see the kernel git commit 30f4d4e.

Detection Methods for CVE-2025-68808

Indicators of Compromise

• Kernel panic or oops messages referencing vidtv driver functions such as vidtv_channel_si_init, vidtv_psi_pat_program_assign, or vidtv_psi_eit_event_assign
• Unexpected system crashes or reboots when DVB/vidtv functionality is in use
• Memory corruption errors in kernel logs related to the media subsystem
• KASAN (Kernel Address Sanitizer) reports indicating use-after-free or double-free in vidtv components

Detection Strategies

• Enable KASAN (Kernel Address Sanitizer) in kernel builds to detect memory corruption issues at runtime
• Monitor kernel logs (dmesg) for BUG or WARNING messages from the vidtv or media subsystems
• Deploy kernel integrity monitoring solutions to detect unexpected crashes or memory anomalies
• Implement audit logging for access to /dev/dvb/ device nodes if vidtv is in use

Monitoring Recommendations

• Configure automated alerting on kernel panic events, particularly those involving media driver components
• Review system logs regularly for signs of memory corruption or unexpected driver behavior
• Consider using SentinelOne's kernel-level monitoring capabilities to detect exploitation attempts targeting memory corruption vulnerabilities
• Monitor for unusual process behavior around DVB device access

How to Mitigate CVE-2025-68808

Immediate Actions Required

• Update to a patched Linux kernel version that includes the fix for this vulnerability
• If the vidtv driver is not required, disable or blacklist the dvb_vidtv_bridge module
• Restrict access to DVB device nodes to trusted users only
• Enable kernel security features such as KASAN in development environments to detect similar issues

Patch Information

The Linux kernel maintainers have released patches to address this vulnerability. The fix ensures that local pointers are properly initialized to NULL after memory ownership is transferred to the PSI tables, preventing the use-after-free and double-free conditions. Multiple stable kernel branches have received this fix:

• Kernel Git Commit 30f4d4e
• Kernel Git Commit 3caa18d
• Kernel Git Commit 98aabfe
• Kernel Git Commit a69c7fd
• Kernel Git Commit fb9bd6d

Workarounds

• Blacklist the vidtv module if Virtual Digital TV functionality is not required: add blacklist dvb_vidtv_bridge to /etc/modprobe.d/blacklist.conf
• Restrict access to /dev/dvb/ devices using udev rules or file permissions to limit potential attack surface
• Deploy kernel live patching solutions if immediate reboots are not feasible in production environments
• Implement mandatory access control (SELinux/AppArmor) policies to restrict access to DVB subsystem components

# Disable vidtv module to mitigate the vulnerability
echo "blacklist dvb_vidtv_bridge" | sudo tee /etc/modprobe.d/blacklist-vidtv.conf
sudo rmmod dvb_vidtv_bridge 2>/dev/null || true
sudo update-initramfs -u