CVE-2026-80793: Linux

EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Linux Linux: from 2.6.12, before 5.10.267 (fixed in 5.10.267); from 5.11, before 5.15.218 (fixed in 5.15.218); from 5.16, before 6.1.185 (fixed in 6.1.185); from 6.2, before 6.6.154 (fixed in 6.6.154); from 6.7, before 6.12.106 (fixed in 6.12.106); from 6.13, before 6.18.47 (fixed in 6.18.47); …

Published 2026-09-04. Last modified 2026-09-04.