CVE-2023-53557 fprobe: Release rethook after the ftrace_ops is unregistered
A use-after-free vulnerability in the Linux kernel fprobe module can cause a general protection fault and system crash during module unloading.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-53557?
CVE-2023-53557 is a high-severity use after free vulnerability in Linux kernel, published on 4 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
fprobe: Release rethook after the ftrace_ops is unregistered
While running bpf selftests it's possible to get following fault:
general protection fault, probably for non-canonical address \ 0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI ... Call Trace: <TASK> fprobe_handler+0xc1/0x270 ? __pfx_bpf_testmod_init+0x10/0x10 ? __pfx_bpf_testmod_init+0x10/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_fentry_test1+0x5/0x10 ? bpf_testmod_init+0x22/0x80 ? do_one_initcall+0x63/0x2e0 ? rcu_is_watching+0xd/0x40 ? kmalloc_trace+0xaf/0xc0 ? do_init_module+0x60/0x250 ? __do_sys_finit_module+0xac/0x120 ? do_syscall_64+0x37/0x90 ? entry_SYSCALL_64_after_hwframe+0x72/0xdc </TASK>
In unregister_fprobe function we can't release fp->rethook while it's possible there are some of its users still running on another cpu.
Moving rethook_free call after fp->ops is unregistered with unregister_ftrace_function call.
Which versions are affected by CVE-2023-53557?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2023-53557?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2023-53557 being exploited?
There is no known exploitation of CVE-2023-53557 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2023-53557, DEBIAN-CVE-2023-53557, GHSA-4jf8-pxjc-f722, UBUNTU-CVE-2023-53557.