CVE-2026-74631 net: smc: fix splice entry lifetime imbalance in smc_rx_splice
A refcount imbalance in the Linux kernel SMC network module allows attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74631?
CVE-2026-74631 is a high-severity use after free vulnerability in Linux, published on 22 Aug 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:
net: smc: fix splice entry lifetime imbalance in smc_rx_splice
smc_rx_splice() passes pages to splice_to_pipe() before taking the references that cover the lifetime of each splice entry. In the VM-backed RMB path, splice_to_pipe() may drop unqueued entries through smc_rx_spd_release(), while queued entries are released later via the pipe buffer callback.
The old post-splice accounting also derives the number of queued VM pages from an offset mutated while building the descriptor, and a multi-page splice pairs one sock_hold() with multiple sock_put() calls.
Take the page and socket references for every candidate entry before splice_to_pipe(), and drop the matching private state, page reference, and socket reference from smc_rx_spd_release() for entries that never get queued. This fixes a refcount imbalance that can underflow page refcounts and trigger a use-after-free.
Which versions are affected by CVE-2026-74631?
How do I fix CVE-2026-74631?
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-2026-74631 being exploited?
There is no known exploitation of CVE-2026-74631 in the wild and no public exploit code.
Sources
Also known as AZL-97118, BELL-CVE-2026-74631, DEBIAN-CVE-2026-74631, GHSA-75cj-q634-phhq, UBUNTU-CVE-2026-74631.