Junos OS: Receipt of a specifically malformed ICMP packet causes an FPC restart

Summary

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. This issue does not affect AFT-based line cards such as the MPC10, MPC11, LC4800, LC9600, and MX304. This issue affects Junos OS:  • all versions before 21.2R3-S9,  • from 21.4 before 21.4R3-S10,  • from 22.2 before 22.2R3-S7,  • from 22.3 before 22.3R3-S4,  • from 22.4 before 22.4R3-S5,  • from 23.2 before 23.2R2-S3,  • from 23.4 before 23.4R2-S3,  • from 24.2 before 24.2R1-S2, 24.2R2.

Timeline

1. Jan 15, 2026, 8:17 PM UTCCVE published
2. Jan 15, 2026, 9:11 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Mar 10, 2026, 10:44 PM UTCRecord last updated

Affected versions

• Juniper Networks Junos OS

  fixed in 21.2R3-S9; From 21.4 · fixed in 21.4R3-S10; From 22.2 · fixed in 22.2R3-S7; From 22.3 · fixed in 22.3R3-S4; From 22.4 · fixed in 22.4R3-S5; From 23.2 · fixed in 23.2R2-S3; From 23.4 · fixed in 23.4R2-S3

References 2