CVE-2026-0203: Junos OS: Receipt of a specifically malformed ICMP packet causes an FPC restart
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.
Affected Software
Remediation
Information
Event History
Frequently Asked Questions
What is the severity of CVE-2026-0203?
CVE-2026-0203 has been rated as a high severity vulnerability due to its potential to cause system disruption.
How do I fix CVE-2026-0203?
To mitigate CVE-2026-0203, upgrade your Junos OS to a version above 21.2R3-S9 or apply the recommended patches.
Who is affected by CVE-2026-0203?
CVE-2026-0203 affects Juniper Networks devices running specific versions of Junos OS, particularly versions prior to 21.2R3-S9.
What type of attack is CVE-2026-0203 associated with?
CVE-2026-0203 is associated with a network-based attack that utilizes malformed ICMP packets to exploit the vulnerability.
Can CVE-2026-0203 lead to unauthorized access?
CVE-2026-0203 does not lead to unauthorized access directly but can cause denial of service through FPC restarts.