CVE-2026-93224 svcrdma: Fix unmatched rn_unregister on failed accept
A use-after-free and memory leak in the Linux kernel's svcrdma module allows attackers to cause denial of service or potentially escalate privileges via failed RDMA accept operations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93224?
CVE-2026-93224 is a high-severity use after free vulnerability in Linux, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
svcrdma: Fix unmatched rn_unregister on failed accept
When svc_rdma_accept() takes the errout path before rpcrdma_rn_register() has succeeded, the existing cleanup block calls rpcrdma_rn_unregister(dev, &newxprt->sc_rn) unconditionally. svcxprt_rdma is kzalloc'd, so on that path sc_rn.rn_index is 0 and sc_rn.rn_done is NULL; the unregister therefore xa_erase()s another caller's slot 0 and performs an unmatched kref_put() on the rpcrdma_device's rd_kref.
The same errout also brackets the cleanup with svc_xprt_get()/ svc_xprt_put() around the kref_init() birth reference. The kref goes 1 -> 2 -> 1 and never reaches 0, so the svcxprt_rdma (and the net/ns_tracker it pinned) is leaked on every failed accept.
rpcrdma_rn_register() writes rn->rn_done last, only after xa_alloc() and kref_get() have both succeeded, so rn_done == NULL is a natural "never registered" sentinel. Guard rpcrdma_rn_unregister() with an early return when rn_done is NULL, and clear rn_done before the matching xa_erase() so a repeated unregister is also a no-op.
With that guard in place, the accept errout drops the kref_init() birth reference via svc_xprt_put(), which dispatches svc_rdma_free(). Teardown of sc_qp, sc_sq_cq, sc_rq_cq, and sc_pd runs under existing IS_ERR/NULL guards in svc_rdma_free(); sc_rn is covered by the new rn_done sentinel; sc_cm_id is non-NULL on every errout path because svc_rdma_accept() dereferences it above the first goto errout.
svc_xprt_free() drops the module reference associated with the freed transport, and svc_handle_xprt() drops its pre-acquired reference when ->xpo_accept() returns NULL. Take a replacement module reference before svc_xprt_put() so the two module_put()s remain balanced.
The rn_done guard also covers svc_rdma_free()'s non-listener call to rpcrdma_rn_unregister() for transports whose register attempt failed or never ran.
Which versions are affected by CVE-2026-93224?
How do I fix CVE-2026-93224?
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-2026-93224 being exploited?
There is no known exploitation of CVE-2026-93224 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93224, DEBIAN-CVE-2026-93224, GHSA-g4hj-w3xr-5rr3, UBUNTU-CVE-2026-93224.