CVE-2026-21903

moderate-risk

Published 2026-01-15

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.

Do I need to act?

0.02% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 6.5/10 Medium

NETWORK / LOW complexity

Affected Products (20)

Junos

Affected Vendors

Juniper

References (2)

Vendor Advisory https://kb.juniper.net/JSA106022

Vendor Advisory https://supportportal.juniper.net/JSA106022

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moderate-risk

Severity 24/34 · High

Exploitability 0/34 · Minimal

Exposure 22/34 · High