CVE-2026-90195 riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args
Missing sign-extension in RISC-V BPF JIT for small signed arguments causes incorrect behavior, potentially leading to logic errors or crashes.
- 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-2026-90195?
CVE-2026-90195 is a vulnerability in Linux, published on 17 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:
riscv, bpf: Fix missing sign-ext for signed 1-byte and 2-byte kfunc args
On RV64, the ABI requires sign-extension for signed 1-byte and 2-byte kfunc args. However, the RV64 JIT currently does not perform sign-extension for such kfunc args.
Before commit 7ce090afbf72 ("bpf: Infer zext_dst based on static register liveness analysis"), state pruning could potentially omit zero-extension of 32-bit subregisters, which inadvertently masked the above issue by making the args appear as if they had been properly sign-extended. After that commit, the problem is exposed, causing the kfunc_call/kfunc_call_test4 selftest to fail.
Fix this by extending the existing sign-extension logic to handle signed 1-byte and 2-byte kfunc args as well.
Which versions are affected by CVE-2026-90195?
How do I fix CVE-2026-90195?
Apply the vendor's patch.
Is CVE-2026-90195 being exploited?
There is no known exploitation of CVE-2026-90195 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-90195, DEBIAN-CVE-2026-90195, GHSA-wm8w-4px2-2hp8, UBUNTU-CVE-2026-90195.