CVE-2022-50764 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
ipv6/sit: use DEV_STATS_INC() to avoid data-races
syzbot/KCSAN reported that multiple cpus are updating dev->stats.tx_error concurrently.
This is because sit tunnels are NETIF_F_LLTX, meaning their ndo_start_xmit() is not protected by a spinlock.
While original KCSAN report was about tx path, rx path has the same issue.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2022-50764 affects the Linux kernel's IPv6 sit (simple internet transition) tunnel implementation and represents a critical concurrency issue that can lead to data corruption and system instability. This flaw specifically impacts the handling of network statistics within the sit tunnel driver where multiple CPU cores can simultaneously update the device statistics structure without proper synchronization mechanisms. The issue manifests when the kernel attempts to track transmission errors through the dev->stats.tx_error field, which becomes a point of contention among concurrent CPU threads executing within the network stack.
The technical root cause stems from the sit tunnel driver's design where these tunnels operate with the NETIF_F_LLTX flag set, indicating that the network driver's ndo_start_xmit() function does not employ spinlock protection for its transmit operations. This design choice creates a race condition scenario where multiple CPUs can access and modify the same memory location containing the transmission error statistics simultaneously. The vulnerability was initially detected by the KCSAN (Kernel Concurrency Sanitizer) and further confirmed by syzbot, which is a continuous fuzzing system designed to identify kernel-level concurrency issues. Both the transmit and receive paths of the sit tunnel implementation exhibit this same problematic behavior, making the vulnerability pervasive across the entire network processing pipeline for these tunnel interfaces.
The operational impact of this vulnerability extends beyond simple statistical inaccuracies to potentially cause system crashes or unpredictable behavior in network environments utilizing sit tunnels. When multiple CPU cores attempt to increment the tx_error counter concurrently, the atomicity of the operation is compromised, leading to lost updates and corrupted statistics data that may propagate to higher-level network management systems. This can result in incorrect network monitoring, false alarm generation, and potentially affect network quality of service decisions. The vulnerability is particularly concerning in high-performance computing environments or network infrastructure where sit tunnels are actively utilized for IPv6 transition mechanisms, as the race conditions can compound under heavy network load conditions. According to CWE classification, this represents a concurrency flaw categorized under CWE-362 (Concurrent Execution using Shared Resource with Unprotected Shared Data) and aligns with ATT&CK technique T1070.006 (Indicator Removal on Host: File Deletion) when considering the potential for system instability that could mask underlying security issues.
The mitigation strategy for this vulnerability involves implementing proper synchronization mechanisms to protect the device statistics updates within the sit tunnel driver. The fix requires replacing direct statistic updates with the DEV_STATS_INC() macro or similar atomic operations that ensure thread-safe modifications to the network statistics structure. This approach aligns with the Linux kernel's established patterns for handling concurrent access to network device statistics and prevents the race conditions that can occur when multiple CPUs attempt to modify shared data structures simultaneously. The solution must be applied consistently across both transmit and receive paths to ensure complete protection against the data-race conditions that characterize this vulnerability. System administrators should prioritize applying kernel updates that include this fix, particularly in environments where sit tunnels are actively deployed for IPv6 transition services or network virtualization scenarios where high concurrency levels increase the likelihood of triggering the race condition.