CVE-2026-90066
Published Sep 17, 2026
Description
In the Linux kernel, the following vulnerability has been resolved: samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify ftrace_direct_multi_init() assigns kthread_run()'s return value to simple_tsk without an IS_ERR() check. When kthread_run() fails it returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads with simple_tsk holding an error pointer. On unload, ftrace_direct_multi_exit() then passes that ERR_PTR to kthread_stop(), leading to a null-pointer-dereference. Check the return value of kthread_run() with IS_ERR(); on failure, unregister the ftrace direct call and propagate the error code.
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References
Other References
https://git.kernel.org/stable/c/626614df9080d7052fbe24dc90b5434717ab7a9f
https://git.kernel.org/stable/c/6727b7618f49401acf373fa3ec5712e2ec52e5cf
https://git.kernel.org/stable/c/7a96b9f6d5ba23dbce66c8a4a242effd4c01a830
https://git.kernel.org/stable/c/98b7b2a29ae87937aa02ab9391543ef8c602cd94
https://git.kernel.org/stable/c/cf839636911d8313f3ecd098329fd0b96499e4cf
Frequently Asked Questions
What is CVE-2026-90066? +
In the Linux kernel, the following vulnerability has been resolved:
samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
ftrace_direct_multi_init() assigns kthread_run()'s return value to
simple_tsk without an IS_ERR() check. When kthread_run() fails it
returns ERR_PTR(-ENOMEM), but init still returns 0, so the module loads
with simple_tsk holding an error pointer. On unload,
ftrace_direct_multi_exit() then passes that ERR_PTR to kthread_stop(),
leading to a null-pointer-dereference.
Check the return value of kthread_run() with IS_ERR(); on failure,
unregister the ftrace direct call and propagate the error code.
How do I check if I'm vulnerable to CVE-2026-90066? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.