CVE-2026-74496 Linux CVE debrief

Who should care

Linux kernel developers and users, cybersecurity teams and researchers, operators of Linux-based systems, and security teams responsible for vulnerability management and patching. These stakeholders should be aware of the potential impact of this vulnerability and take steps to mitigate it, such as applying the patch from the Linux kernel repository and reviewing system logs for potential exploitation attempts. Additionally, they should consider implementing compensating controls, such as monitoring and asset inventory, to detect and prevent potential attacks. The vulnerability can be exploited by a concurrent receive operation, which can lead to a denial-of-service or potentially allow an attacker to execute arbitrary code. Therefore, it is essential to prioritize patching and mitigation efforts to prevent potential attacks. Linux distribution maintainers and cloud providers may also need to review and update their configurations to prevent similar vulnerabilities in the future. Furthermore, security researchers and penetration testers may be interested in testing the vulnerability and developing exploits to improve defensive measures. Overall, a broad range of stakeholders should be aware of this vulnerability and take proactive steps to mitigate its impact. The vulnerability affects Linux kernel versions and may be exploitable in various Linux distributions and deployments. Affected stakeholders should verify their systems and apply patches or mitigations as needed to prevent potential attacks. The vulnerability highlights the importance of secure coding practices, thorough testing, and timely patching to prevent use-after-free vulnerabilities in critical infrastructure. By prioritizing patching and mitigation efforts, stakeholders can reduce the risk of exploitation and protect their systems from potential attacks. The vulnerability also underscores the need for ongoing vulnerability research and development of defensive measures to stay ahead of emerging threats. By staying informed and proactive, stakeholders can minimize the impact of this vulnerability and improve the overall security posture of their systems and deployments. Linux kernel developers and

Technical summary

The vulnerability is caused by a use-after-free error in the fou_create() function. The function publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data. A concurrent receive can then dereference the freed object in fou_from_sock(). The failure is reachable when local port 0 is requested. Each socket binds to a different ephemeral port, but fou_cfg_cmp() compares the requested port 0 and reports -EALREADY once an entry already exists. The vulnerability has been resolved by releasing the tunnel socket before freeing fou so sk_user_data is cleared first, and defer reclamation with kfree_rcu() to protect concurrent RCU readers.

Defensive priority

High

Recommended defensive actions

• Apply the patch from the Linux kernel repository
• Review and update Linux kernel configurations to prevent similar vulnerabilities
• Monitor system logs for potential exploitation attempts
• Perform a thorough review of system configurations to ensure they align with security best practices
• Implement additional monitoring and logging to detect potential exploitation attempts
• Conduct a thorough asset inventory to identify potentially affected systems
• Review and update incident response plans to include procedures for responding to potential exploitation attempts

Evidence notes

The vulnerability is caused by a use-after-free error in the fou_create() function. The function publishes struct fou through sk_user_data before adding the new FOU port to the per-netns list. If fou_add_to_port_list() fails, the error path frees fou while it is still reachable through sk_user_data. A concurrent receive can then dereference the freed object in fou_from_sock().

Official resources