CVE-2026-99227

Status: UPDATED  |  Advisory ID: CVE-2026-99227

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

io_uring/waitid: prevent cancel reference wrap

io_waitid packs the cancellation state into bit 31 of ->refs and uses

bits 30:0 as a 31-bit reference counter:

#define IO_WAITID_CANCEL_FLAG BIT(31)

#define IO_WAITID_REF_MASK GENMASK(30, 0)

__io_waitid_cancel() marks a request canceled, then increments the low

bits of ->refs to claim completion ownership. When another path owns the

request, the increment remains even though cancellation returns false.

The request remains discoverable by cancellation, so repeated failed

attempts can wrap the 31-bit reference field to zero. A later

cancellation can claim ownership and complete the request a second time.

Use atomic_fetch_or() when setting the cancel flag and inspect the old

flag value. The first cancel attempt continues to the existing ownership

increment, preserving its wake and issuer handoff semantics. Later

attempts see the cancel flag and return without incrementing the

reference field.

This makes repeated failed cancellation attempts idempotent while

leaving the first-cancel state transitions unchanged. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References