Juniper Junos OS: 2026-01 Security Bulletin: Junos OS: Receipt of a specifically malformed ICMP packet causes an FPC restart (JSA104294) (CVE-2026-0203)

An Improper Handling of Exceptional Conditions vulnerability in packet processing of Juniper Networks Junos OS allows an unauthenticated, network-adjacent attacker sending a specifically malformed ICMP packet to cause an FPC to crash and restart, resulting in a Denial of Service (DoS).When an ICMP packet is received with a specifically malformed IP header value, the FPC receiving the packet crashes and restarts. Due to the specific type of malformed packet, adjacent upstream routers would not forward the packet, limiting the attack surface to adjacent networks.This issue only affects ICMPv4. ICMPv6 is not vulnerable to this issue.