CVE-2026-90248

A moderate severity flaw was found in the Linux kernel's network scheduler traffic classifier code (net/sched: cls_api). The flaw affects the kernel and kernel-rt packages in Red Hat Enterprise Linux 8, 9, and 10, Red Hat In-Vehicle OS 2, and the RHEL CoreOS images used by OpenShift Container Platform 4. In tc_new_tfilter(), when concurrent requests race to insert a traffic control classifier at the same chain and priority, the request that loses the race follows an error path that incorrectly tears down and unlinks the live classifier that the winning request had already created and advertised via RTM_NEWTFILTER. A local attacker able to configure traffic control filters could exploit this race condition to silently remove an active network classifier, disrupting network traffic classification and causing a denial of service. Only availability is affected; confidentiality and integrity are not impacted (CVSS 3.1: 5.5, AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Red Hat Enterprise Linux 7 is not affected because the vulnerable code is not present in that release, and Red Hat Enterprise Linux 6 Extended Lifecycle Support is out of support status (OOSS). For the affected products, the fix is deferred: because this is a moderate-severity, local, availability-only race condition, it is slated to be addressed in a future update rather than an immediate erratum. The residual risk is that a local user could disrupt traffic-control classification on an affected system.