CVE-2025-40075 in Linux
Summary
by MITRE • 10/28/2025
In the Linux kernel, the following vulnerability has been resolved:
tcp_metrics: use dst_dev_net_rcu()
Replace three dst_dev() with a lockdep enabled helper.
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Analysis
by VulDB Data Team • 02/15/2026
The vulnerability identified as CVE-2025-40075 resides within the Linux kernel's TCP metrics subsystem, specifically addressing a concurrency and locking issue that could potentially lead to system instability or security implications. This flaw manifests in the tcp_metrics module where the kernel attempts to access network device information in a manner that lacks proper locking mechanisms. The vulnerability stems from the use of dst_dev() function calls which do not provide adequate protection against concurrent access scenarios, creating potential race conditions that could be exploited by malicious actors to disrupt system operations or potentially escalate privileges.
The technical flaw involves the replacement of three instances of dst_dev() with the dst_dev_net_rcu() helper function, which incorporates lockdep (lock dependency) enabled mechanisms for proper synchronization. This change addresses a fundamental issue where direct access to network device information could occur without appropriate locking, particularly in multi-threaded environments where multiple processes or kernel threads might simultaneously attempt to access or modify device-related data structures. The dst_dev() function, while functional, lacks the necessary synchronization primitives to prevent concurrent access issues that could result in data corruption or system crashes. The introduction of dst_dev_net_rcu() provides the required RCU (Read-Copy-Update) protection that ensures safe concurrent access to network device information.
The operational impact of this vulnerability extends beyond simple system stability concerns to encompass potential security implications within networked environments. When multiple threads access network device information simultaneously without proper locking, the kernel's memory management and network stack operations could become compromised. This could manifest as system crashes, network connectivity disruptions, or in more severe cases, allow for privilege escalation attacks that leverage the race conditions to gain elevated system access. The vulnerability particularly affects systems running Linux kernels where TCP metrics are actively utilized, which includes virtually all modern networked systems, making it a critical security concern for enterprise environments and network infrastructure.
Mitigation strategies for CVE-2025-40075 primarily involve upgrading to a patched kernel version that implements the dst_dev_net_rcu() helper function throughout the tcp_metrics subsystem. System administrators should prioritize applying this update across all production environments, particularly those handling high volumes of network traffic or operating in security-sensitive contexts. The fix aligns with best practices outlined in the Common Weakness Enumeration (CWE) category CWE-362, which addresses concurrent execution using locks and other synchronization mechanisms. Additionally, this vulnerability and its resolution demonstrate principles from the ATT&CK framework's privilege escalation tactics, where improper locking mechanisms can create opportunities for attackers to exploit system weaknesses. Organizations should also implement monitoring for unusual network behavior or system crashes that might indicate exploitation attempts, while maintaining comprehensive patch management processes to ensure all kernel components remain up-to-date with security fixes. The change represents a fundamental improvement in kernel stability and security through proper synchronization mechanisms that prevent the race conditions that could otherwise compromise system integrity.