CVE-2026-21903: Junos OS: Subscribing to telemetry sensors at scale causes all FPCs to crash
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 Software
Remediation
Information
Event History
Frequently Asked Questions
What is the severity of CVE-2026-21903?
CVE-2026-21903 has a high severity rating due to its potential to cause Denial-of-Service (DoS) by crashing all FPCs.
How do I fix CVE-2026-21903?
To fix CVE-2026-21903, update Junos OS to versions beyond 22.4R3-S7, 23.2R2-S4, or 23.4R2.
Who is affected by CVE-2026-21903?
CVE-2026-21903 affects devices running vulnerable versions of Juniper Networks Junos OS.
What type of attack does CVE-2026-21903 enable?
CVE-2026-21903 enables a Denial-of-Service attack due to a stack-based buffer overflow.
What components of Junos OS are impacted by CVE-2026-21903?
The Packet Forwarding Engine (pfe) is the component impacted by CVE-2026-21903.