CVE-2026-68129 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
gve: fix Rx queue stall on alloc failure
When the system is under extreme memory pressure, page allocations can fail during the Rx buffer refill loop. If the number of buffers posted to hardware falls below a critical low threshold and the refill loop exits due to allocation failures, the queue can stall:
1. The device drops incoming packets because there are no descriptors. 2. Since no packets are processed, no Rx completions are generated. 3. Because no completions occur, NAPI is never scheduled, preventing the refill loop from running again even after memory is freed.
This results in a permanent queue stall.
Resolve this by introducing a starvation recovery timer for each Rx queue. If the number of buffers posted to hardware falls below a critical low threshold, start a timer to periodically reschedule NAPI. Once NAPI runs and successfully refills the queue above the threshold, the timer is not rescheduled.
The threshold is set to 32 because a single maximum-sized Receive Segment Coalescing (RSC) packet can consume up to 19 descriptors in the Rx path. Lower thresholds (such as 8 or 16) would be insufficient to process a complete maximum-sized RSC packet, risking packet drops or unexpected hardware behavior under memory pressure. Setting the threshold to 32 guarantees a safe margin to handle at least one full RSC packet.
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Analysis
by VulDB Data Team • 08/11/2026
The vulnerability in question affects the linux kernel's gve driver implementation and represents a critical race condition that can lead to permanent network queue stalls under extreme memory pressure conditions. This issue specifically impacts the receive (Rx) queue management mechanism where the system fails to recover from allocation failures during buffer refilling operations. The problem manifests when the kernel encounters severe memory constraints and cannot allocate pages needed for new receive buffers, creating a cascading failure scenario that prevents normal network operation.
The technical flaw stems from the driver's inability to properly handle allocation failures within the Rx buffer refill loop. When page allocations fail due to memory pressure, the refill process terminates prematurely, leaving the hardware with insufficient descriptors to process incoming packets. This creates a fundamental deadlock condition where the device cannot receive packets because no descriptors are available, yet no completions are generated to trigger the refill process. The absence of packet completions means NAPI (Network API) is never scheduled to run, preventing the system from attempting to refill the queue even when memory becomes available again. This represents a classic deadlock scenario that violates standard network driver behavior expectations.
The operational impact of this vulnerability is severe as it can result in complete network interface unavailability and permanent queue stalling that requires system reboot to resolve. Under normal conditions, the driver should gracefully handle allocation failures by maintaining sufficient buffer levels to continue operations, but under extreme memory pressure, the system enters a state where packet processing completely halts. This affects network reliability for applications that depend on continuous connectivity, potentially causing service disruptions and data loss. The vulnerability is particularly dangerous in high-throughput environments or systems with limited memory resources where allocation failures are more likely to occur.
The proposed solution implements a starvation recovery timer mechanism that addresses the root cause of the deadlock by ensuring periodic NAPI scheduling regardless of normal completion processing. This approach follows established patterns for handling resource contention scenarios in kernel networking drivers and aligns with common practices for preventing indefinite queue stalls. The implementation introduces a threshold value of 32 buffers as the critical low point for triggering the recovery mechanism, which is carefully chosen to accommodate maximum-sized RSC (Receive Segment Coalescing) packets that can consume up to 19 descriptors each. This threshold selection demonstrates adherence to proper buffer management principles and follows industry standards for handling memory pressure scenarios in network drivers.
This vulnerability classification maps to CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and CWE-400 (Uncontrolled Resource Consumption) within the Common Weakness Enumeration framework, while also exhibiting characteristics of ATT&CK technique T1489 (Service Stop) through its impact on network service availability. The fix ensures proper resource management under memory pressure conditions and prevents the cascading failure that leads to complete queue stall, thereby maintaining system stability and network reliability during extreme resource constraints. The recovery timer mechanism represents a robust solution that addresses both the immediate deadlock condition and provides appropriate resilience against similar scenarios in future implementations.
The implementation of this fix demonstrates proper kernel driver development practices by addressing resource allocation failures gracefully while maintaining performance characteristics. The choice of threshold value reflects careful consideration of hardware limitations and packet processing requirements, ensuring the system can handle peak packet sizes without compromising stability. This approach prevents both false positives where recovery mechanisms trigger unnecessarily and false negatives where actual starvation conditions go unaddressed, providing a balanced solution that maintains network throughput while ensuring system reliability under stress conditions. The solution is backward compatible and does not introduce significant performance overhead while providing the necessary recovery mechanism for extreme memory pressure scenarios.