CVE-2026-89985 memcg: keep folio's objcg same as its node
A race condition in Linux kernel memory cgroup reparenting can cause lock mismatches, potentially leading to system crashes or 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-2026-89985?
CVE-2026-89985 is a high-severity 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:
memcg: keep folio's objcg same as its node
memcg_reparent_objcgs() has an inherent assumption that a folio's objcg is the objcg of the folio's node. Folio migration across nodes breaks that assumption: the new folio simply inherits the old folio's objcg while living on a different node.
Once the assumption is broken, the reparenting of the folio's objcg and the reparenting of the folio's LRU list are no longer atomic. memcg_reparent_objcgs() handles one node per iteration and drops all the locks in between, so the objcg gets reparented in the iteration for the objcg's node while the LRU list gets spliced in the iteration for the folio's node. Any LRU operation on that folio in between resolves its lruvec through the objcg, and thus takes the lru_lock of the wrong memcg, not the lru_lock of the list the folio is actually on.
Fix this by selecting the objcg by folio_nid() at charge time, and by re-deriving it for the destination node in mem_cgroup_migrate() and mem_cgroup_replace_folio().
Which versions are affected by CVE-2026-89985?
How do I fix CVE-2026-89985?
Apply the vendor's patch.
Is CVE-2026-89985 being exploited?
There is no known exploitation of CVE-2026-89985 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-89985, GHSA-5r45-xw38-xrg8, UBUNTU-CVE-2026-89985.