CVE-2025-38107: 
Linux Kernel vulnerability analysis and mitigation

A race condition vulnerability was discovered in the Linux kernel's ETS (Enhanced Transmission Selection) subsystem, identified as CVE-2025-38107. The vulnerability was reported by Gerrard Tai and affects the etsqdiscchange() function when the SFQ perturb timer fires at an inopportune time. The issue was disclosed on July 3, 2025 (NVD, CVE).

The vulnerability occurs due to a race condition in the following sequence: On CPU 0 - lock root, qdisctreeflushbacklog(), unlock root; while simultaneously on CPU 1 - qdiscput(), lock root, rehash, qdisctreereduce_backlog(). This sequence can lead to an underflow of a parent's qlen. The technical assessment indicates that the vulnerability exists in the network scheduling component of the Linux kernel (Debian Tracker).

The vulnerability can be exploited to underflow a parent's qlen (queue length), potentially affecting network traffic management and quality of service configurations in Linux systems (NVD).

The fix involves replacing qdisctreeflushbacklog() with qdiscpurge_queue(), ensuring all packets are purged from the qdisc before releasing the lock. This modification prevents the race condition by maintaining proper synchronization (NVD).