CVE-2026-74543 Linux CVE debrief

Who should care

Linux kernel developers, administrators who manage Linux-based systems, and security teams responsible for vulnerability management and patch application. These stakeholders should review and apply the patch to fix the memory leak vulnerability and monitor systems for potential memory leaks.

Why it matters

A memory leak vulnerability was found in the Linux kernel's UDP tunnel NIC offload code. The vulnerability can lead to potential denial-of-service (DoS) attacks if exploited. Linux kernel developers and administrators who manage Linux-based systems should review and apply the patch to fix the vulnerability.

• Memory leak vulnerability can lead to potential denial-of-service (DoS) attacks
• Exploitation of this vulnerability requires authentication and access to the system
• Verification of patch application and system monitoring are necessary to prevent exploitation

Technical summary

The vulnerability is caused by an early return in udp_tunnel_nic_unregister() when device registration fails. This leads to a memory leak of the struct udp_tunnel_nic allocated in udp_tunnel_nic_alloc(). The fix involves removing the early return and synchronously canceling any pending work with cancel_delayed_work_sync() before freeing the struct. This change prevents permanent memory leaks in the Linux kernel's UDP tunnel NIC offload code. Linux kernel developers and administrators should review and apply the patch.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the patch to fix the memory leak vulnerability
• Update Linux kernel to the latest version
• Monitor system for potential memory leaks
• Perform vulnerability assessment to identify potential exposure
• Implement compensating controls for exposed systems
• Track exceptions and retest remediated assets
• Review relevant monitoring, detection, and logs for exposed assets

Evidence notes

The vulnerability was reported by syzbot and fixed by removing the early return in udp_tunnel_nic_unregister(). The fix also involves switching udp_tunnel_nic_device_sync_work() to rtnl_trylock() and requeueing the work with a 1 jiffy delay if RTNL is contended. This change aims to prevent high CPU contention while waiting for RTNL lock. Linux kernel developers should verify patch application and monitor systems for potential memory leaks.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.