In the Linux kernel, the following vulnerability has been resolved:
cuse: wait for pending RCU callbacks on module exit
Since commit 053fc4f755ad ("fuse: fix UAF in rcu pathwalks"), fuse_conn_put() frees the fuse_conn through call_rcu() rather than synchronously. For cuse, fc->release is cuse_fc_release(), which lives in the cuse module. If the module is removed before the RCU grace period ends, the callback jumps into freed module memory:
userspace / module unload | RCU softirq
close(/dev/cuse) |
cuse_channel_release() |
fuse_dev_release() |
fuse_conn_put(fch->conn) |
call_rcu(delayed_release) ------+---> callback queued
|
rmmod cuse |
cuse_exit() |
cuse_channel_destroy() |
... |
return |
|
<module text freed> |
| rcu_do_batch()
| delayed_release()
| fc->release()
| -> cuse_fc_release()
| ^^^ freed text!
The freed module text is unmapped by vfree(), so the jump into the
stale callback triggers a page-fault Oops. If the virtual address
is subsequently reused, the callback could execute unrelated code
(undefined behaviour).
Fix this by calling rcu_barrier() in cuse_exit() so that any pending
fuse_conn release callback completes before the module is removed.
{
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90140.json"
}