# CVE-2026-97974: ipv6: null-check fib6_node before accessing in __ip6_del_rt_siblings()

> A local attacker can trigger a null pointer dereference in the Linux kernel IPv6 routing code, causing a system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-97974, DEBIAN-CVE-2026-97974, GHSA-2j2r-fxqg-mc3v, UBUNTU-CVE-2026-97974

## What is CVE-2026-97974?

CVE-2026-97974 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ipv6: null-check fib6_node before accessing in __ip6_del_rt_siblings()

syzbot reported a null-ptr-deref in __ip6_del_rt_siblings() [0].

The stack trace hinted towards a null dereference of rt->fib6_node when
fn->leaf is accessed in __ip6_del_rt_siblings(). With
RTNL_FLAG_DOIT_UNLOCKED set, inet6_rtm_delroute() operations run
concurrently without acquiring the RTNL lock. In ip6_route_del(), the
route lookup happens under rcu_read_lock() without acquiring
table->tb6_lock.

Between ip6_route_del() looking up the route and __ip6_del_rt_siblings()
acquiring table->tb6_lock, another thread can modify the routing table.
For example, when an ECMP route is replaced via RTM_NEWROUTE with
NLM_F_REPLACE, fib6_add_rt2node() unlinks all old siblings and sets
iter->fib6_node = NULL. A reproducer was found that triggers this [1].

Add a check to ensure rt->fib6_node is non-null before accessing it.

[0]
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
RIP: 0010:__ip6_del_rt_siblings+0x31e/0x7c0 net/ipv6/route.c:4056
Call Trace:
 <TASK>
 ip6_route_del+0x1054/0x1110 net/ipv6/route.c:4232
 inet6_rtm_delroute+0x5d7/0x6d0 net/ipv6/route.c:5669
 rtnetlink_rcv_msg+0x802/0xc00 net/core/rtnetlink.c:7132
 netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x7f5/0x990 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
 sock_sendmsg_nosec+0x13a/0x180 net/socket.c:800
 __sock_sendmsg net/socket.c:815 [inline]
 ____sys_sendmsg+0x565/0x870 net/socket.c:2713
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2767
 __sys_sendmsg net/socket.c:2799 [inline]
 __do_sys_sendmsg net/socket.c:2804 [inline]
 __se_sys_sendmsg net/socket.c:2802 [inline]
 __x64_sys_sendmsg+0x1b7/0x290 net/socket.c:2802
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
 </TASK>

[1] https://gist.github.com/NamanGulati/0766a1159b6ca61928faaf87425ff899

## Which versions are affected by CVE-2026-97974?


## How do I fix CVE-2026-97974?

Apply the vendor's patch.

## Is CVE-2026-97974 being exploited?

There is no known exploitation of CVE-2026-97974 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97974 and fix it if it is affected.

What it is: CVE-2026-97974 is a vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97974 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-97974/ (Markdown: https://insights.sbomify.com/CVE-2026-97974/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97974
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97974
- OSV: https://osv.dev/vulnerability/CVE-2026-97974

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97974/
Summaries are generated and may contain mistakes; the official description above is the record.