Preface: Syzbot has begun to report kernel findings to LKML in 2017. Syzbot is a continuous kernel build / fuzz / report aggregation system.

Background: Linux has two mechanisms for setting routes, one is fib, and the other is routing generated by dynamic. fib uses route (man 8 route) to specify a static route table. What net/ipv4/route[.]c does is dynamic generate routing hash to speed up route decision.

Vulnerability details: In the Linux kernel, the following vulnerability has been resolved: ipv4: check for NULL idev in ip_route_use_hint() . syzbot was able to trigger a NULL deref in fib_validate_source() in an old tree .

It appears the bug exists in latest trees. All calls to __in_dev_get_rcu() must be checked for a NULL result.

Official announcement: Please refer to the link for details – https://nvd.nist.gov/vuln/detail/CVE-2024-36008