CVE-2025-71126 Linux CVE debrief

Who should care

Linux kernel developers and maintainers, network administrators, and users of Linux-based systems should be aware of this vulnerability and take necessary actions to mitigate it. The issue affects the Linux kernel's MPTCP implementation and could potentially lead to deadlocks, causing system crashes or freezes. Affected parties should review and update the MPTCP implementation to avoid deadlocks and monitor for potential exploit attempts. Additionally, applying patches provided by the Linux kernel maintainers can help to resolve the issue. The vulnerability has a high defensive priority, and affected parties should take immediate action to mitigate it. The issue is caused by a missing lock nesting notation in the MPTCP fallback critical section, and the packet scheduler could attempt a reinjection after receiving an MP_FAIL and before the infinite map has been transmitted, causing a deadlock since MPTCP needs to do the reinjection atomically from WRT fallback. The issue has been resolved by explicitly avoiding the reinjection in the critical scenario. Evidence notes suggest that the issue is caused by a missing lock nesting notation in the MPTCP fallback critical section, and the packet scheduler could attempt a reinjection after receiving an MP_FAIL and before the infinite map has been transmitted, causing a deadlock since MPTCP needs to do the reinjection atomically from WRT fallback. The issue has been resolved by explicitly avoiding the reinjection in the critical scenario. The vulnerability affects Linux kernel developers and maintainers, network administrators, and users of Linux-based systems. The issue affects the Linux kernel's MPTCP implementation and could potentially lead to deadlocks, causing system crashes or freezes. Affected parties should review and update the MPTCP implementation to avoid deadlocks and monitor for potential exploit attempts. Additionally, applying patches provided by the Linux kernel maintainers can help to resolve the issue. The vulnerability has a high defensive priority, and affected parties should take immediate action to mitigate it. The issue is caused by a missing lock nesting notation in the MPTCP fallback critical  

Technical summary

The Linux kernel's MPTCP implementation has a deadlock vulnerability. The issue occurs when the packet scheduler attempts to reinject a packet after receiving an MP_FAIL and before the infinite map has been transmitted, causing a deadlock. This is due to a missing lock nesting notation in the MPTCP fallback critical section. The issue has been resolved by explicitly avoiding the reinjection in the critical scenario. The vulnerability affects Linux kernel developers and maintainers, network administrators, and users of Linux-based systems.

Defensive priority

High

Recommended defensive actions

• Apply patches provided by the Linux kernel maintainers
• Review and update MPTCP implementation to avoid deadlocks
• Monitor for potential exploit attempts
• Perform a thorough review of the system configuration to identify potential vulnerabilities
• Implement additional monitoring and logging to detect potential attacks
• Conduct a thorough asset inventory to identify affected systems
• Verify that all necessary patches have been applied and are up-to-date

Evidence notes

The issue is caused by a missing lock nesting notation in the MPTCP fallback critical section. The packet scheduler could attempt a reinjection after receiving an MP_FAIL and before the infinite map has been transmitted, causing a deadlock since MPTCP needs to do the reinjection atomically from WRT fallback.

Official resources