CVE-2026-64535: Linux

Critical severity, CVSS 9.8. EPSS: 0.5% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: nvmet-tcp: Fix potential UAF when ddgst mismatch Shivam Kumar found via vulnerability testing: When data digest is enabled on an NVMe/TCP connection and a digest mismatch occurs on a non-final H2C_DATA PDU during an R2T-based data transfer, the digest error handler in nvmet_tcp_try_recv_ddgst() calls nvmet_req_uninit() — which performs percpu_ref_put() on the submission queue — but does NOT mark the command as completed. It does not set cqe->status, does not modify rbytes_done, and does not clear any flag. When the subsequent fatal error triggers queue teardown, nvmet_tcp_uninit_data_in_cmds() iterates all commands, checks nvmet_tcp_need_data_in() for each one, and finds that the already-uninited command still appears to need data (because rbytes_done < transfer_len and cqe->status == 0). It therefore calls nvmet_req_uninit() a second time on the same command — a double percpu_ref_put against a single percpu_ref_get.

Affected products

• Linux Linux: from 5.10.20, before 5.10.265 (fixed in 5.10.265); from 5.11.3, before 5.12 (fixed in 5.12); from 5.12, before 5.15.216 (fixed in 5.15.216); from 5.16, before 6.1.178 (fixed in 6.1.178); from 6.2, before 6.6.145 (fixed in 6.6.145); from 6.7, before 6.12.97 (fixed in 6.12.97); …

Published 2026-07-27. Last modified 2026-08-19.