CVE-2026-74260 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_dup_netdev: add nf_dev_xmit_recursion*() helpers and use them
Update nft_dup and nft_fwd to use the nf_dev_xmit_recursion() helpers. This patch also disables BH when transmitting the skb to address a possible migration to different CPU leading to imbalanced decrementation of the recursion counters.
This is modeled after Florian Westphal's dev_xmit_recursion*() API available since commit 97cdcf37b57e ("net: place xmit recursion in softnet data") according to its current state in the tree.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability addressed in this linux kernel update relates to a potential recursion issue within the netfilter subsystem, specifically affecting network packet forwarding and duplication operations. The problem manifests in the nf_dup_netdev functionality where improper handling of packet transmission can lead to race conditions and counter management issues during network processing. This flaw exists within the nft_dup and nft_fwd netfilter table operations that handle packet duplication and forwarding respectively, creating a scenario where recursion counters may become imbalanced due to improper CPU migration handling during packet transmission.
The technical implementation of this vulnerability stems from the lack of proper recursion tracking mechanisms when packets are transmitted through network devices within the netfilter framework. When packets are duplicated or forwarded using nft_dup and nft_fwd operations, the system relies on recursion counters to track transmission depth and prevent infinite loops. However, without proper synchronization mechanisms, packet transmission can migrate between different CPU cores during processing, leading to inconsistent decrementation of these recursion counters. This creates a potential for stack corruption, memory inconsistency issues, and denial of service conditions that could be exploited by malicious actors.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromising system stability and network functionality. Attackers could exploit the recursion counter imbalance to cause system crashes, packet loss, or create conditions where legitimate network traffic becomes disrupted. The issue particularly affects systems heavily utilizing netfilter rules for packet manipulation, filtering, or forwarding operations, making it a significant concern for network appliances, firewalls, and systems implementing complex network policies. The vulnerability essentially creates a race condition in the softnet data structure where transmission recursion tracking becomes inconsistent across CPU cores.
The mitigation strategy implemented in this patch involves introducing new nf_dev_xmit_recursion() helper functions that properly manage the recursion counter operations during packet transmission. These helpers ensure that bottom-half (BH) processing is disabled during transmission, preventing the possibility of packets migrating to different CPU cores while the recursion counters are being modified. This approach mirrors the established dev_xmit_recursion() API pattern introduced in commit 97cdcf37b57e, which specifically addresses the same class of issues by centralizing recursion management within the softnet data structure. The solution follows established kernel development patterns for managing concurrent access to shared resources and provides a robust mechanism for handling packet transmission recursion without introducing additional complexity or performance overhead.
This vulnerability aligns with common security concerns identified in the CWE database under categories related to improper handling of recursion and race conditions in kernel space operations. The fix addresses specific attack vectors listed in MITRE ATT&CK framework within the privilege escalation and denial of service categories, where adversaries could leverage such recursion issues to cause system instability or gain elevated privileges through carefully crafted network packet manipulation. The implementation follows best practices for kernel development by utilizing existing infrastructure patterns rather than introducing novel approaches that might create additional vulnerabilities while ensuring proper synchronization mechanisms are in place to prevent the class of issues being addressed.