CVE-2025-68362 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
wifi: rtl818x: rtl8187: Fix potential buffer underflow in rtl8187_rx_cb()
The rtl8187_rx_cb() calculates the rx descriptor header address by subtracting its size from the skb tail pointer. However, it does not validate if the received packet (skb->len from urb->actual_length) is large enough to contain this header.
If a truncated packet is received, this will lead to a buffer underflow, reading memory before the start of the skb data area, and causing a kernel panic.
Add length checks for both rtl8187 and rtl8187b descriptor headers before attempting to access them, dropping the packet cleanly if the check fails.
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Analysis
by VulDB Data Team • 01/12/2026
The vulnerability identified as CVE-2025-68362 represents a critical buffer underflow condition within the Linux kernel's wireless networking subsystem, specifically affecting the rtl818x driver family including the rtl8187 module. This flaw exists in the rtl8187_rx_cb() function which processes received wireless packets and handles the calculation of receive descriptor header addresses. The implementation performs a mathematical operation by subtracting the descriptor header size from the skb (socket buffer) tail pointer to determine where the header should be located. However, the function fails to validate whether the actual received packet data contains sufficient bytes to accommodate this calculated header position, creating a fundamental security gap in the kernel's packet processing logic.
The technical nature of this vulnerability stems from inadequate input validation within the wireless driver's receive path processing. When a truncated packet is received through the USB interface, the function proceeds to calculate a memory address that falls before the legitimate start of the socket buffer data area. This results in reading from memory locations that are not properly allocated for the packet data, effectively causing a buffer underflow condition. The absence of proper bounds checking means that the kernel attempts to access memory regions that may contain sensitive data, kernel structures, or other critical information that should remain protected from unauthorized access. This type of vulnerability directly maps to CWE-129, which describes improper validation of the length of input data, and represents a classic example of insufficient boundary checking in kernel space code.
The operational impact of this vulnerability is severe and potentially catastrophic for systems running affected Linux kernels. When triggered, the buffer underflow condition causes an immediate kernel panic, resulting in a system crash and complete service disruption. This renders the affected wireless networking capabilities unavailable and can lead to denial of service conditions that may affect the entire system stability. The vulnerability is particularly concerning because it can be exploited through crafted wireless packets transmitted over the air, making it remotely exploitable by adversaries within wireless range of the vulnerable device. The attack requires no special privileges and can be executed by any entity capable of transmitting wireless frames to the target system, potentially allowing for remote system compromise or persistent denial of service attacks against wireless infrastructure.
The mitigation strategy for this vulnerability involves implementing proper length validation checks for both rtl8187 and rtl8187b descriptor headers before attempting any memory access operations. The fix requires adding explicit checks to verify that the received packet length, as indicated by skb->len from urb->actual_length, is sufficient to contain the calculated descriptor header position. When these validation checks fail, the system should drop the packet cleanly rather than attempting to process it, preventing the buffer underflow condition from occurring. This approach aligns with the principle of defensive programming and follows the ATT&CK framework's mitigation strategies for kernel-level vulnerabilities by ensuring proper input validation and error handling. System administrators should prioritize applying the relevant kernel updates that contain this fix, particularly in environments where wireless networking is critical and where the risk of wireless-based attacks cannot be adequately mitigated through network segmentation or other security controls. The vulnerability demonstrates the importance of rigorous input validation in kernel space code and highlights the need for comprehensive testing of wireless driver implementations against malformed packet scenarios.