CyberRota Analysis
AI-GeneratedThe vulnerability in the Linux kernel affects the IPv4 packet fragmentation process, specifically in the `ip_do_fragment()` function, where it fails to properly handle undersized Maximum Transmission Units (MTUs). This can lead to a denial-of-service condition, as the system may enter a state of infinite fragmentation without making progress, potentially triggering a soft lockup. Organizations using affected Linux systems, particularly those managing network traffic with customized MTU settings, should prioritize applying the fix to mitigate this risk.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: reject undersized MTUs in ip_do_fragment() ip_do_fragment() subtracts the IPv4 header length from the effective MTU and passes the resulting payload MTU to ip_frag_next(). If the effective MTU is smaller than hlen + 8, ip_frag_next() rounds the fragment payload length down to zero. The fragmentation state then never makes forward progress: state->left, state->ptr and state->offset stay unchanged while ip_do_fragment() keeps allocating and transmitting header-only fragments until the softlockup detector fires. This is reproducible with a route installed using "mtu lock 20", but it is also reproducible without route MTU lock, for example by forwarding a packet to a device whose MTU is 20. Fix it in ip_do_fragment() by rejecting mtu < hlen + 8 with -EMSGSIZE, matching the existing IPv6 fragmentation check.