CVE-2026-97922 tracing: Free histogram var refs regardless of how often they are referenced
A memory leak in Linux kernel histogram triggers allows local attackers to exhaust memory by removing triggers with multiple variable references.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-97922?
CVE-2026-97922 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 var refs regardless of how often they are referenced
Using the same variable three or more times in one hist trigger leaks the variable reference and its strings when the trigger is removed.
commit 656fe2ba85e8 ("tracing: Use hist trigger's var_ref array to destroy var_refs") made a trigger's var_refs[] array the only owner of a var ref: destroy_hist_field() returns early for HIST_FIELD_FL_VAR_REF, so the field expressions never destroy one. One entry, freed once, no count needed.
commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") then made repeated references share one object and added a count of them. Only the increment side exists, since those expressions still return early and never drop a reference, so __destroy_hist_field() sees how many references were created rather than how many are left. It frees when the decremented count is 0 or 1, so two references work and three or more leak.
Sharing kept one array entry per object, and create_var_ref() searches and appends within a single trigger, so nothing outside it holds the object. Removing a trigger whose variables are still referenced is already refused by check_var_refs() with -EBUSY. Drop the count and free unconditionally.
Which versions are affected by CVE-2026-97922?
How do I fix CVE-2026-97922?
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-2026-97922 being exploited?
There is no known exploitation of CVE-2026-97922 in the wild and no public exploit code.
Sources
Also known as AZL-104196, BELL-CVE-2026-97922, DEBIAN-CVE-2026-97922, GHSA-m6gp-f257-gxcp, UBUNTU-CVE-2026-97922.