CVE-2026-43121

The record

In the Linux kernel, the following vulnerability has been resolved: io_uring/zcrx: fix user_ref race between scrub and refill paths The io_zcrx_put_niov_uref() function uses a non-atomic check-then-decrement pattern (atomic_read followed by separate atomic_dec) to manipulate user_refs. This is serialized against other callers by rq_lock, but io_zcrx_scrub() modifies the same counter with atomic_xchg() WITHOUT holding rq_lock. On SMP systems, the following race exists: CPU0 (refill, holds rq_lock) CPU1 (scrub, no rq_lock) put_niov_uref: atomic_read(uref) - 1 // window opens atomic_xchg(uref, 0) - 1 return_niov_freelist(niov) [PUSH #1] // window closes atomic_dec(uref) - wraps to -1 returns true return_niov(niov) return_niov_freelist(niov) [PUSH #2: DOUBLE-FREE] The same niov is pushed to the freelist twice, causing free_count to exceed nr_iovs. Subsequent freelist pushes then perform an out-of-bounds write (a u32 value) past the kvmalloc'd freelist array into the adjacent slab object. Fix this by replacing the non-atomic read-then-dec in io_zcrx_put_niov_uref() with an atomic_try_cmpxchg loop that atomically tests and decrements user_refs. This makes the operation safe against concurrent atomic_xchg from scrub without requiring scrub to acquire rq_lock. [pavel: removed a warning and a comment]

Affected packages

Related vulnerabilities

• CVE-2026-114641 Traefik 2.11.x before 2.11.58 and 3.x before 3.7.14 contains a race condition in NTLM and… CWE-362
• CVE-2026-109279 ImageMagick before 6.9.13-57 and 7.x before 7.1.2-32 lacks proper synchronization when… CWE-362
• CVE-2026-97032 HTTP/2 servers could end up crashing due to inadvertently modifying its HPACK encoder… CWE-362
• CVE-2026-98163 In the Linux kernel, the following vulnerability has been resolved: cgroup: Avoid… CWE-362
• CVE-2026-98146 In the Linux kernel, the following vulnerability has been resolved: accel/amdxdna: Remove… CWE-362
• CVE-2026-98153 In the Linux kernel, the following vulnerability has been resolved: nvme: fix racy access… CWE-362
• CVE-2026-98130 In the Linux kernel, the following vulnerability has been resolved: sctp: fix a TOCTOU… CWE-362
• CVE-2026-98115 In the Linux kernel, the following vulnerability has been resolved: ksmbd: safely drain… CWE-362