CVE-2026-21903: Juniper Junos

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service (DoS). Subscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart. The issue was not seen when YANG packages for the specific sensors were installed. This issue affects Junos OS:  * all versions before 22.4R3-S7, * 23.2 version before 23.2R2-S4, * 23.4 versions before 23.4R2.

Affected products

• Juniper Junos: before 22.4 (fixed in 22.4); version 22.4 only; version 23.2 only; version 23.4 only

Published 2026-01-15. Last modified 2026-06-17.