CVE-2026-68411 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211_hwsim: clamp virtio RX length before skb_put
hwsim_virtio_rx_work() passes the virtqueue used-ring length reported by the device straight to skb_put() on a fixed-size receive skb. A backend reporting a length larger than the skb tailroom drives skb_put() past the buffer end and hits skb_over_panic() -- a host-triggerable guest panic (denial of service).
Clamp the length to the skb's available room before skb_put(). A conforming device never reports more than the posted buffer size, so valid frames are unaffected; a truncated over-report then fails the length/header checks in hwsim_virtio_handle_cmd() and is dropped, so truncating rather than dropping here cannot be turned into a parsing problem.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability resides within the linux kernel's mac80211 hardware simulator implementation known as hwsim which emulates wireless network interfaces for testing and development purposes. This particular flaw exists in the virtio-based receive path handling mechanism that manages data transmission between guest virtual machines and the simulated wireless hardware. The issue manifests when processing incoming network frames through the hwsim_virtio_rx_work() function which processes received packets from virtualized wireless devices.
The technical implementation flaw stems from improper bounds checking during packet buffer manipulation within the wireless simulation framework. Specifically, the function directly utilizes the length value reported by the virtio device's used-ring without validating whether this reported length exceeds the allocated buffer space within the socket buffer structure. When a malicious or misbehaving backend device reports an excessive length value that surpasses the available tailroom in the pre-allocated receive skb, the skb_put() function attempts to write beyond the buffer boundaries, triggering the kernel's skb_over_panic() mechanism that results in immediate system panic and denial of service.
This vulnerability represents a classic buffer overflow condition within kernel networking code that aligns with CWE-121 and CWE-787 categories related to improper bounds checking. The attack vector involves an unprivileged guest operating system or virtual machine that can manipulate the virtio device interface to report malformed packet lengths, effectively creating a host-triggered denial of service scenario. The impact extends beyond simple availability disruption as this condition can be exploited to crash the entire kernel subsystem managing wireless communications.
The fix implemented addresses this by introducing explicit length clamping before calling skb_put(), ensuring that the reported device length never exceeds the available buffer space within the socket buffer. This defensive programming approach prevents the kernel panic while maintaining compatibility with legitimate network traffic. The solution leverages standard kernel memory management principles and follows established practices for handling virtio device communications where device-reported values must always be validated against allocated buffer boundaries. Valid frames that conform to proper network protocols remain unaffected as the length validation occurs before any packet processing, ensuring that only malformed over-reporting scenarios are handled gracefully rather than causing system crashes. This mitigation strategy aligns with ATT&CK technique T1499.004 for network denial of service and demonstrates proper input validation practices essential for kernel security.
The vulnerability demonstrates how virtualization environments can introduce complex attack surfaces where guest operating systems may abuse device interface implementations to compromise host stability. The fix emphasizes the importance of defensive programming in kernel space where all external inputs, including those from virtualized hardware interfaces, must undergo rigorous validation before being processed. This particular issue highlights the need for robust buffer management practices in high-performance networking code that handles multiple layers of abstraction between physical hardware and virtual device emulations.