CVE-2026-72392 ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump
A local attacker can trigger a kernel panic via a race condition in IPv6 FIB dumping, causing a denial of service.
- 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
What is CVE-2026-72392?
CVE-2026-72392 is a vulnerability in Linux, published on 15 Aug 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: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump
inet6_dump_fib() saves its progress in cb->args[1] as a positional index within the current hash chain. Between batches, a concurrent fib6_new_table() can insert a new table at the chain head, shifting all existing entries. The saved index then lands on a different table, causing fib6_dump_table() to set w->root to the wrong table while w->node still points into the previous one. fib6_walk_continue() dereferences w->node->parent (NULL) and panics:
BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:fib6_walk_continue+0x6e/0x170 Call Trace: <TASK> fib6_dump_table.isra.0+0xc5/0x240 inet6_dump_fib+0xf6/0x420 rtnl_dumpit+0x30/0xa0 netlink_dump+0x15b/0x460 netlink_recvmsg+0x1d6/0x2a0 ____sys_recvmsg+0x17a/0x190
Fix by storing tb->tb6_id in cb->args[1] instead of a positional index. On resume, skip entries until the id matches; a concurrent head-insert can never match the saved id, so the walker always resumes on the correct table.
Which versions are affected by CVE-2026-72392?
How do I fix CVE-2026-72392?
Apply the vendor's patch.
Is CVE-2026-72392 being exploited?
There is no known exploitation of CVE-2026-72392 in the wild and no public exploit code.
Sources
Also known as AZL-96446, BELL-CVE-2026-72392, DEBIAN-CVE-2026-72392, GHSA-gqrm-563w-26qf, UBUNTU-CVE-2026-72392.