CVE-2026-89545 sunrpc: defer rq_argp and rq_resp free until after RCU grace period
A use-after-free in the Linux kernel's sunrpc module allows attackers to potentially execute code or escalate privileges via race conditions in RCU handling.
- 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-2026-89545?
CVE-2026-89545 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: defer rq_argp and rq_resp free until after RCU grace period
svc_rqst_free() frees rqstp->rq_argp and rqstp->rq_resp synchronously via kfree(), but defers the rqstp struct free via kfree_rcu(). After svc_exit_thread() calls list_del_rcu() and svc_rqst_free(), there is a window where RCU readers that started before list_del_rcu() can still traverse the thread list and find the rqstp. These readers (e.g. nfsd_nl_rpc_status_get_dumpit()) dereference rqstp->rq_argp, which has already been freed — a use-after-free.
Fix this by moving the kfree of rq_argp and rq_resp into an explicit call_rcu() callback alongside the struct free. Resources not accessed by RCU readers (bvec, buffer pages, scratch folio, auth_data) remain synchronously freed.
Which versions are affected by CVE-2026-89545?
How do I fix CVE-2026-89545?
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-2026-89545 being exploited?
There is no known exploitation of CVE-2026-89545 in the wild and no public exploit code.
Sources
Also known as AZL-100280, BELL-CVE-2026-89545, DEBIAN-CVE-2026-89545, GHSA-43p7-fx92-rp4x, UBUNTU-CVE-2026-89545.