UBUNTU-CVE-2026-89480: High severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: nvme-tcp: reject a read that transferred too few bytes nvmetcprecvdata() 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 nvmetcprequest has no receive-side counter, queue->dataremaining is per queue, and blkmqendrequest() completes for blkrqbytes(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 NVMETCPFDATASUCCESS paths and in nvmetcpprocessnvmecqe(). 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 REQOPREAD 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-5.15to a version that resolves this vulnerability.Fixed in 5.15.0-1119.126~20.04.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-42.42.1 - Compensating control
In the NVMe/TCP driver, count the bytes received for each REQ_OP_READ and reject or fail the request when the count does not equal the requested length. Apply this validation at both nvme_tcp_recv_data() NVME_TCP_F_DATA_SUCCESS paths and in nvme_tcp_process_nvme_cqe(); ensure the success check evaluates req->status after shifting it right by one.
Event History
Frequently Asked Questions
Who needs to be trusted or compromised for exploitation to occur?
An NVMe/TCP controller must return a short successful C2HData response for a read. The attack is network-reachable and requires no privileges or user interaction on the affected host.
What is the practical impact of a successful exploit?
A 4096-byte read can be completed after only 512 bytes are received. The remaining bytes returned to user space may contain data that was already present in the page, potentially disclosing stale memory contents.
Which request types are covered by the described fix?
The added length validation is limited to REQ_OP_READ requests, where the expected length is derived from the sectors covered by the request. Passthrough commands are not included in this check because their length is not derived the same way.