CVE-2026-90002 ftrace: Take trace_array reference before accessing its ftrace_ops
A race condition in the Linux kernel ftrace subsystem allows a use-after-free, leading to a kernel crash and denial of service.
- 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-2026-90002?
CVE-2026-90002 is a high-severity use after free vulnerability in Linux, published on 16 Sep 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:
ftrace: Take trace_array reference before accessing its ftrace_ops
The trace instance files set_ftrace_filter and set_ftrace_notrace was updated to work with specific trace instances (trace_arrays). The issue is that when these files are opened, there is a small race window where it will use the ftrace_ops from the inode->private pointer to get a reference to the trace_array and then take its reference. The problem is that the ftrace_ops itself could be freed. If the rmdir on the instance happens at the same time the set_ftrace_filter file is opened, the rmdir could have also freed the ftrace_ops and referencing it will cause a use-after-free bug and crash the kernel.
Instead, pass in the trace_array as the file private data (NULL for the top level instance), and then pass both the trace_array and the ftrace_ops to the ftrace_regex_open() function. If the trace_array is NULL, then it just uses the ftrace_ops without the need to take its reference (like normal). If the ftrace_ops is NULL, that is only the case for the top level instance and the global_ops can be used.
This allows the trace_array to have its reference incremented before touching the ftrace_ops that could also be freed when the instance is.
Which versions are affected by CVE-2026-90002?
How do I fix CVE-2026-90002?
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-2026-90002 being exploited?
There is no known exploitation of CVE-2026-90002 in the wild and no public exploit code.
Sources
Also known as AZL-101693, BELL-CVE-2026-90002, DEBIAN-CVE-2026-90002, GHSA-hxw4-9m57-prf4, UBUNTU-CVE-2026-90002.