CVE-2026-80715 in Linux
Summary
by MITRE • 08/28/2026
In the Linux kernel, the following vulnerability has been resolved:
igc: remove napi_synchronize() in igc_down()
When an AF_XDP zero-copy application is killed abruptly, the XSK pool is torn down but NAPI keeps polling. igc_clean_rx_irq_zc() then returns the full budget on every poll, so napi_complete_done() never clears NAPI_STATE_SCHED.
igc_down() calls napi_synchronize() before napi_disable(), so it spins forever waiting for that bit and the interface never goes down. Drop the napi_synchronize() and let napi_disable() do the job -- it sets NAPI_STATE_DISABLE, which forces the stuck poll to complete. Reorder it ahead of igc_set_queue_napi() so the NAPI mapping is cleared only after polling has stopped, matching the recent igb fix b1e067240379.
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Analysis
by VulDB Data Team • 08/28/2026
The vulnerability identified in the Linux kernel's Intel Gigabit Ethernet driver involves a deadlock condition within the network interface shutdown sequence when interacting with AF_XDP zero-copy applications. This issue manifests specifically when an application utilizing XSK (AF_XDP socket) pools is terminated abruptly, leading to a state where the networking subsystem fails to properly release resources and bring down the network interface. The root cause lies in the interaction between the NAPI polling mechanism and the driver's teardown logic during this specific failure scenario.
When an AF_XDP zero-copy application crashes or is killed without proper cleanup, the associated XSK pool is torn down by the kernel while the Network Interface Polling (NAPI) subsystem continues to attempt processing packets. The function igc_clean_rx_irq_zc(), which handles incoming packet reception for this driver, detects that there are no more buffers available in the now-defunct pool and consequently returns the full budget on every poll invocation. Because it always returns a value equal to or greater than the requested budget, the kernel's NAPI core interprets this as work still being pending and never clears the NAPI_STATE_SCHED flag. This creates a persistent loop where the driver believes there is always more work to do, preventing any state transition that would allow for normal interface shutdown procedures.
The critical flaw occurs within the igc_down() function, which is responsible for disabling the network device. The original implementation called napi_synchronize() before invoking napi_disable(). The napi_synchronize() function attempts to wait until all currently running NAPI poll instances have completed their execution by spinning on the NAPI_STATE_SCHED bit. However, because the stuck poll loop described above never clears this flag due to the infinite budget return behavior of igc_clean_rx_irq_zc(), the call to napi_synchronize() enters an indefinite spin loop. This results in a hard lockup where the interface remains up and unresponsive, effectively causing a denial of service for any traffic attempting to use that network adapter until a system reboot occurs.
The resolution involves removing the problematic napi_synchronize() call from igc_down(). Instead, the fix relies on the inherent behavior of napi_disable(), which sets the NAPI_STATE_DISABLE flag. This state change forces the stuck poll loop in igc_clean_rx_irq_zc() to terminate because the kernel's NAPI core will no longer schedule polls for a device marked as disabled. By allowing napi_disable() to handle the synchronization, the driver avoids the infinite spin and allows the interface to shut down correctly. Additionally, the fix reorders operations so that napi_synchronize is not used at all in this context, ensuring that the NAPI mapping is cleared only after polling has definitively stopped, aligning with recent fixes applied to similar drivers like igb for consistency and stability.
From a security perspective, this vulnerability represents a local denial of service condition triggered by application behavior rather than malicious exploitation of code execution flaws. It falls under CWE-835, which covers loops that do not terminate correctly due to logic errors in state management or resource cleanup. In the context of MITRE ATT&CK, while primarily an availability issue, such kernel-level hangs can be leveraged for local denial-of-service attacks if an attacker has the ability to spawn and abruptly kill AF_XDP applications on a target system. The impact is significant as it renders network connectivity unusable without administrative intervention or rebooting the host machine.
Mitigation strategies focus primarily on applying the upstream kernel patch that removes the napi_synchronize() call from igc_down(). System administrators should ensure their Linux kernels are updated to versions containing this fix, particularly if they run workloads involving high-performance networking via AF_XDP. For environments where immediate patching is not possible, monitoring for processes using XSK pools and ensuring graceful termination of such applications can reduce the likelihood of triggering the deadlock condition. Furthermore, implementing robust application-level error handling that ensures proper cleanup of network resources before process exit serves as a preventive measure against this specific class of kernel state corruption.