CVE-2021-31372: Juniper Junos

High severity, CVSS 8.8. EPSS: 1.2% chance of exploitation in the next 30 days.

An Improper Input Validation vulnerability in J-Web of Juniper Networks Junos OS allows a locally authenticated J-Web attacker to escalate their privileges to root over the target device. This issue affects: Juniper Networks Junos OS All versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R3-S9; 19.1 versions prior to 19.1R3-S6; 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R3-S3; 19.4 versions prior to 19.4R3-S5; 20.1 versions prior to 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2, 21.1R3; 21.2 versions prior to 21.2R1-S1, 21.2R2;

Affected products

• Juniper Junos: up to and including 18.2; version 18.3 only; version 18.4 only; version 19.1 only; version 19.2 only; version 19.3 only; …

Published 2021-10-19. Last modified 2026-06-17.