CVE-2026-53243
Published: June 25, 2026· Updated: Jun 30, 2026
Official Description
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.
Technical Analysis
CVE-2026-53243 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
Affected Vendors & Products
Exploit & PoC Resources
All References (2)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-53243 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts