CVE-2026-74477 uprobes: Fix NULL pointer dereference in hprobe_expire()
A local attacker can trigger a kernel crash by forking a task with a pending uretprobe, causing a NULL pointer dereference in the Linux kernel.
- 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-2026-74477?
CVE-2026-74477 is a vulnerability in Linux, published on 15 Aug 2026. 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:
uprobes: Fix NULL pointer dereference in hprobe_expire()
Forking a task that has a pending uretprobe can oops the kernel with a NULL pointer dereference in the clone() path:
BUG: kernel NULL pointer dereference, address: 0000000000000018 Oops: 0002 [#1] SMP NOPTI RIP: 0010:hprobe_expire CR2: 0000000000000018 Call Trace: uprobe_copy_process copy_process kernel_clone __x64_sys_clone do_syscall_64 entry_SYSCALL_64_after_hwframe
This was found on real hosts on Meta fleet.
I've got the impression that this is what is happening:
CPU 1 CPU 2 (traced task) ----- ------------------- hit uprobe, prepare_uretprobe(): hprobe LEASED, refcount >= 1 uprobe_unregister() put_uprobe(): refcount -> 0 fork() -> dup_utask() hprobe_expire(hprobe, true) try_get_uprobe() -> NULL get_uprobe(NULL) <-- Oops
Only take the extra reference when the uprobe is non-NULL; a NULL means it is gone and is the correct value to return.
Which versions are affected by CVE-2026-74477?
How do I fix CVE-2026-74477?
Apply the vendor's patch.
Is CVE-2026-74477 being exploited?
There is no known exploitation of CVE-2026-74477 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74477, DEBIAN-CVE-2026-74477, GHSA-pgww-xqqj-6xv5, UBUNTU-CVE-2026-74477.