CVE-2025-21655: Linux Kernel

Medium severity, CVSS 4.7. EPSS: 0.3% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: io_uring/eventfd: ensure io_eventfd_signal() defers another RCU period io_eventfd_do_signal() is invoked from an RCU callback, but when dropping the reference to the io_ev_fd, it calls io_eventfd_free() directly if the refcount drops to zero. This isn't correct, as any potential freeing of the io_ev_fd should be deferred another RCU grace period. Just call io_eventfd_put() rather than open-code the dec-and-test and free, which will correctly defer it another RCU grace period.

Affected products

• Linux Linux Kernel: from 6.1, before 6.1.125 (fixed in 6.1.125); from 6.2, before 6.6.72 (fixed in 6.6.72); from 6.7, before 6.12.10 (fixed in 6.12.10); version 6.13 only

Published 2025-01-20. Last modified 2026-07-30.