What is CVE-2026-21910?

CVE-2026-21910 is a medium-severity vulnerability in Juniper Ex4000, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 6.5/10. Published 2026-01-15.

How severe is CVE-2026-21910?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Juniper Ex4000

CVE-2026-21910

An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on EX4k Series and QFX5k Series platforms allows an unauthenticated network-adjacent attacker flapping…

EPSS: 0.002 (15.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Juniper Ex4000
Juniper Ex4100
Juniper Ex4100-f
Juniper Ex4100-h
Juniper Ex4300
Juniper Ex4400
Juniper Ex4600
Juniper Ex4650
Juniper Junos — versions 21.4, 22.2, 22.4
Juniper Qfx5110

Weakness classification (CWE)

CWE-754 — Improper Check for Unusual or Exceptional Conditions

References

sirt@juniper.net (vendor-advisory, Vendor Advisory)
sirt@juniper.net (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21910?: CVE-2026-21910 is a medium-severity vulnerability in Juniper Ex4000, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 6.5/10. Published 2026-01-15.
How severe is CVE-2026-21910?: Medium severity. CVSS v3 base score is 6.5 out of 10.