CVE-2026-89548 SUNRPC: always drain cache_cleaner before destroying a cache_detail
A use-after-free in the Linux kernel SUNRPC subsystem allows attackers to execute arbitrary code or escalate privileges during network namespace teardown.
- 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-2026-89548?
CVE-2026-89548 is a high-severity use after free vulnerability in Linux, published on 11 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:
SUNRPC: always drain cache_cleaner before destroying a cache_detail
sunrpc_destroy_cache_detail() only cancels the global cache_cleaner delayed_work when cache_list is empty. During per-netns teardown cache_list is never empty because init_net's caches remain registered, so the cancel never fires. After unlink, the caller proceeds to cache_destroy_net() which kfrees the cache_detail while cache_clean() may still hold a dangling pointer to it. The result is a use-after-free: cache_dequeue() takes cd->queue_lock on freed memory, and cache_put() dereferences cd->cache_put as a function pointer from freed slab.
Drop the list_empty guard so that cancel_delayed_work_sync() always runs, ensuring any in-flight cache_clean() completes before the cache_detail is freed. Re-arm the cleaner afterwards if other caches are still registered.
Which versions are affected by CVE-2026-89548?
How do I fix CVE-2026-89548?
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-2026-89548 being exploited?
There is no known exploitation of CVE-2026-89548 in the wild and no public exploit code.
Sources
Also known as AZL-100743, BELL-CVE-2026-89548, DEBIAN-CVE-2026-89548, GHSA-3g7j-4hj7-8rgc, UBUNTU-CVE-2026-89548.