CVE-2026-21903 MEDIUM

CVE-2026-21903: Junos OS: Subscribing to telemetry sensors at scale causes all FPCs to crash

Vendor Juniper Networks
Product Junos OS
Weakness CWE-121
Published January 15, 2026
Last update January 15, 2026

CVSS base score

6.5/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

January 15, 2026 CVE published
January 15, 2026 Record updated