CVE-2026-90140
UnknownSummary
In the Linux kernel, the cuse module has a use-after-free vulnerability during module unload. fuse_conn_put() frees fuse_conn via call_rcu(), and if the cuse module is removed before the RCU grace period ends, the callback may execute freed module memory, causing a page fault or undefined behavior.
Risk Assessment
The risk includes system crash (Oops) or potential execution of unrelated code, which could compromise system integrity. However, exploitation requires local access and the ability to unload the module, limiting exploitability.
Recommendation
It is recommended to immediately update the Linux kernel to a version containing the fix that adds rcu_barrier() in cuse_exit(). If updating is not possible, avoid unloading the cuse module in production environments.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS