CVE-2026-99072 ipv4: stop route notification sizing when nexthop group shrinks
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99072?
CVE-2026-99072 is a vulnerability in Linux, published on 23 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ipv4: stop route notification sizing when nexthop group shrinks
Commit 680aea08e78c ("net: ipv4: Emit notification when fib hardware flags are changed") added an RCU-only fib_nlmsg_size() call for asynchronous hardware flag notifications.
fib_nlmsg_size() checks fib_info_num_path() before each iteration, then fib_info_nhc() independently reloads nh->nh_grp. If RTM_NEWNEXTHOP replaces a group with fewer paths between those loads, fib_info_nhc() returns NULL and fib_nexthop_nlmsg_size() dereferences it.
Stop sizing when the indexed path is absent. Nexthop groups are dense, so the current snapshot has no later path.
Which versions are affected by CVE-2026-99072?
How do I fix CVE-2026-99072?
Upgrade to a fixed version.
Is CVE-2026-99072 being exploited?
There is no known exploitation of CVE-2026-99072 in the wild and no public exploit code.
Sources
Also known as AZL-110966, BELL-CVE-2026-99072, DEBIAN-CVE-2026-99072, GHSA-wrfx-ch9c-5jj2, UBUNTU-CVE-2026-99072.