CVE-2024-41090: Linux Kernel Buffer Overflow Vulnerability

CVE-2024-41090 Overview

CVE-2024-41090 is an Out-of-Bounds Read vulnerability in the Linux kernel's TAP (network tap) device driver. The vulnerability exists in the tap_get_user_xdp() function, which fails to properly verify the validity of frame length before processing network frames. This missing verification allows corrupted socket buffers (skb) to be transmitted downstream, potentially causing out-of-bounds memory access or inconsistent header metadata in the network stack.

The vulnerability arises because the tap_get_user_xdp() path does not include the same frame length validation that exists in the alternative tap_get_user() function. When a short frame (less than Ethernet header size of 14 bytes) is processed through the vulnerable code path, the skb_set_network_header() function incorrectly assumes the frame size is at least ETH_HLEN, leading to memory access issues.

Critical Impact

Local attackers with low privileges can exploit this vulnerability to cause out-of-bounds memory reads, potentially leading to information disclosure or system instability through corrupted network packet handling.

Affected Products

• Linux Kernel (multiple versions)
• Systems using TAP/TUN virtual network devices
• Virtualization environments utilizing kernel TAP interfaces

Discovery Timeline

• July 29, 2024 - CVE-2024-41090 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2024-41090

Vulnerability Analysis

The vulnerability is classified as CWE-125 (Out-of-Bounds Read) and affects the Linux kernel's TAP device implementation. The issue occurs when processing XDP (eXpress Data Path) frames through the tap_get_user_xdp() function. Unlike its counterpart tap_get_user(), this code path lacks proper validation to ensure incoming frames meet the minimum Ethernet header size requirement.

When a malicious or malformed short frame is received, the code proceeds to call skb_set_network_header() with the assumption that the frame contains at least ETH_HLEN (14 bytes) of data. This incorrect assumption can result in the network header pointer referencing memory beyond the actual buffer boundaries, creating an out-of-bounds read condition.

The impact extends beyond simple memory reads—the corrupted skb metadata can propagate through the network stack, causing unpredictable behavior in lower network layers that rely on accurate header length information.

Root Cause

The root cause is a missing input validation check in the tap_get_user_xdp() function. The commit that introduced XDP support for TAP devices failed to include the frame length verification that was already present in tap_get_user(). This oversight allowed frames shorter than ETH_HLEN to bypass validation and enter the processing pipeline, violating the implicit assumption that all Ethernet frames contain at least a complete header.

Attack Vector

This vulnerability requires local access to the system and low-privilege user access. An attacker with the ability to send crafted network frames through a TAP device interface can exploit this vulnerability. The attack scenario involves:

1. Gaining access to a TAP device interface (commonly available in virtualization or container environments)
2. Sending specially crafted short frames (less than 14 bytes) through the XDP path
3. Triggering the out-of-bounds read when the kernel attempts to set network headers
4. Potentially causing information disclosure from kernel memory or system instability

The vulnerability does not require user interaction and operates within the local system boundary, making it particularly relevant for multi-tenant or containerized environments where TAP devices are commonly used.

Detection Methods for CVE-2024-41090

Indicators of Compromise

• Unexpected kernel crashes or panics related to network subsystem operations
• Anomalous TAP device activity with unusually short frame transmissions
• Kernel log messages indicating skb corruption or network header inconsistencies
• Memory access violations in the network stack during TAP operations

Detection Strategies

• Monitor kernel logs for TAP-related errors using dmesg filtering for "tap" and "skb" messages
• Deploy kernel tracing tools (ftrace, eBPF) to monitor tap_get_user_xdp() function calls with abnormal frame sizes
• Implement network traffic analysis on TAP interfaces to detect frames shorter than standard Ethernet minimum
• Use kernel debugging features like KASAN (Kernel Address Sanitizer) to detect out-of-bounds memory accesses

Monitoring Recommendations

• Enable kernel audit logging for network device operations in sensitive environments
• Configure system monitoring to alert on unexpected TAP device behavior patterns
• Deploy endpoint detection solutions capable of monitoring kernel-level network operations
• Review virtualization and container orchestration logs for unusual network interface activity

How to Mitigate CVE-2024-41090

Immediate Actions Required

• Update Linux kernel to a patched version containing the frame length validation fix
• Review and restrict access to TAP device interfaces where possible
• Audit systems using TAP devices for potential exploitation attempts
• Apply distribution-specific security updates (see Debian LTS announcement for Debian-based systems)

Patch Information

Multiple kernel commits have been released to address this vulnerability. The fix adds proper frame length verification in tap_get_user_xdp() to drop any frame shorter than the Ethernet header size, matching the existing behavior in tap_get_user().

Relevant patch commits:

• Kernel Commit 73d462a
• Kernel Commit 7431144
• Kernel Commit 8be915f
• Kernel Commit aa6a570
• Kernel Commit e1a786b
• Kernel Commit e5e5e63
• Kernel Commit ed7f2af
• Kernel Commit ee93e6d

For Debian-based distributions, refer to the Debian LTS Announcement for specific package updates.

Workarounds

• Restrict TAP device creation and access using Linux capabilities and namespace isolation
• Implement network filtering rules to drop malformed frames before they reach TAP interfaces
• Use SELinux or AppArmor policies to limit processes that can interact with TAP devices
• Consider disabling XDP on TAP devices if not required for operational needs

# Restrict TAP device access to specific users/groups
chmod 600 /dev/net/tun
chown root:kvm /dev/net/tun

# Verify kernel version includes the patch
uname -r
# Check for patched versions in your distribution's security advisories