CVE-2026-97923 tracing: Free histogram the var ref when its initialization fails
A memory leak in the Linux kernel tracing subsystem allows local attackers to cause denial of service by triggering histogram initialization failures.
- 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-2026-97923?
CVE-2026-97923 is a memory corruption vulnerability in Linux, published on 25 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:
tracing: Free histogram the var ref when its initialization fails
create_var_ref() allocates a VAR_REF hist_field and then calls init_var_ref() to fill it in. When that fails the field is leaked.
commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy var_refs") made destroy_hist_field() return early for HIST_FIELD_FL_VAR_REF, since var refs are freed by walking the trigger's var_refs[] array instead. create_var_ref() adds the field to that array only after init_var_ref() has succeeded, so on this path the field is in neither place and nothing frees it. The call was correct when it was written, before var refs were taken out of destroy_hist_field().
init_var_ref() cannot free it either. The caller owns the field, so init_var_ref() undoes only its own string allocations and leaves the field alone. Freeing it there would leave create_var_ref() passing freed memory to destroy_hist_field(), which reads its flags.
Call __destroy_hist_field(), which frees the field without consulting the flag.
Which versions are affected by CVE-2026-97923?
How do I fix CVE-2026-97923?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-97923 being exploited?
There is no known exploitation of CVE-2026-97923 in the wild and no public exploit code.
Sources
Also known as AZL-104586, BELL-CVE-2026-97923, DEBIAN-CVE-2026-97923, GHSA-28hv-8h97-8cx6, UBUNTU-CVE-2026-97923.