In the Linux kernel, the following vulnerability has been resolved: rseq: Fix using an uninitialized stack variable in rseq_exit_user_update() There is an bug in which an uninitialized stack variable is used in rseq_exit_user_update() as reported by syzbot: BUG: KMSAN: kernel-infoleak in rseq_set_ids_get_csaddr include/linux/rseq_entry.h:502 [inline] The local variable: struct rseq_ids ids = { .cpu_id = task_cpu(t), .mm_cid = task_mm_cid(t), .node_id = cpu_to_node(ids.cpu_id), }; According to the C standard, the evaluation order of expressions in an initializer list is indeterminately sequenced. The compiler (Clang, in this KMSAN build) evaluates `cpu_to_node(ids.cpu_id)` *before* `ids.cpu_id` is initialized with `task_cpu(t)`. This is fixed by moving the assignment of ids.node_id outside the structure initialization.

A flaw was found in the Linux kernel. An uninitialized stack variable in the `rseq_exit_user_update()` function can lead to an information leak. This occurs due to an indeterminate sequencing of expressions during the initialization of the `rseq_ids` structure, where `ids.node_id` is assigned using an uninitialized `ids.cpu_id`. A local attacker could potentially exploit this to gain sensitive kernel information.

Red Hat Enterprise Linux 10 Not affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Not affected kernel Red Hat Enterprise Linux 9 Not affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-53243 https://nvd.nist.gov/vuln/detail/CVE-2026-53243 https://lore.kernel.org/linux-cve-announce/2026062511-CVE-2026-53243-0e70@gregkh/T