CVE-2026-63864

A flaw was found in the Linux kernel's Berkeley Packet Filter (BPF) verifier. The visit_tailcall_insn function, which is part of the BPF program validation process, failed to check and propagate error return values. This oversight could lead to an unhandled error condition within the kernel, potentially affecting system stability or integrity. The vulnerability stems from a missing error check, which is a fundamental security mechanism.

This vulnerability is rated as Moderate severity for Red Hat because exploitation is restricted to local users and requires privileges to load extended Berkeley Packet Filter (eBPF) programs to trigger an unhandled kernel verifier error. By default, standard Red Hat Enterprise Linux releases disable unprivileged eBPF execution, substantially limiting the attack surface to administrative accounts possessing CAP_BPF or CAP_SYS_ADMIN capabilities. Furthermore, enterprise versions such as RHEL 8 and 9 do not ship the introduced tail-call validation code, confining exposure exclusively to newer kernel streams.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.