A bug in the Linux kernel tracing subsystem could cause an infinite recursion when RCU events are traced with the stack trace trigger enabled. The recursion occurs because the stack trace code calls back into RCU, which then triggers the stack trace again, exhausting the kernel stack and resulting in a kernel panic or system crash. The recent fix introduces recursion protection bits so that retracing is prevented, mitigating the denial of service potential. Without the patch, an attacker with the ability to enable kernel tracing may be able to voluntarily trigger this crash and render the system unavailable.

This issue affected all Linux kernel releases prior to the inclusion of the recursion protection fix, including the early release candidates of kernel 6.19 (rc1 through rc4) and earlier stable releases. It applies to any system running the standard Linux kernel where RCU tracing is enabled and the stack trace trigger is active.

The CVSS score of 5.5 indicates a medium severity vulnerability. The EPSS score of less than 1% suggests a low likelihood of exploitation in the wild, and the vulnerability is not listed in CISA's KEV catalog. The attack vector most likely requires a privileged or root user to enable the specific tracing configuration that triggers the recursion. An unprivileged user cannot exploit the flaw unless kernel configuration permits arbitrary kernel tracing.