CVE-2026-89480 nvme-tcp: reject a read that transferred too few bytes
A malicious NVMe controller can return fewer bytes than requested, causing the kernel to expose uninitialized memory to user space.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89480?
CVE-2026-89480 is a high-severity vulnerability in Linux, published on 11 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:
nvme-tcp: reject a read that transferred too few bytes
nvme_tcp_recv_data() completes a request once the current C2HData PDU has been consumed. Nothing compares the total bytes received against the length the command asked for: struct nvme_tcp_request has no receive-side counter, queue->data_remaining is per queue, and blk_mq_end_request() completes for blk_rq_bytes(rq) unconditionally with no residual concept anywhere above.
A controller can therefore answer a 4096-byte read with 512 bytes and have it reported as a complete read; user space then gets 4096 bytes of which 3584 are whatever was already in the page. I reproduced that with a test target.
Count the bytes received and refuse to complete a successful read whose count does not match, at the two NVME_TCP_F_DATA_SUCCESS paths and in nvme_tcp_process_nvme_cqe(). The success test shifts req->status right by one, because the driver keeps the wire value there and shifts it on completion, so the check must see what the completion path will see. Only REQ_OP_READ is checked, because there the length comes from the sectors the request covers; a passthrough command is built by its submitter, which picks both command and buffer, so the kernel has nothing to compare against.
Which versions are affected by CVE-2026-89480?
How do I fix CVE-2026-89480?
Apply the vendor's patch.
Is CVE-2026-89480 being exploited?
There is no known exploitation of CVE-2026-89480 in the wild and no public exploit code.
Sources
Also known as AZL-100577, BELL-CVE-2026-89480, DEBIAN-CVE-2026-89480, GHSA-p53f-q495-p25h, UBUNTU-CVE-2026-89480.