Improper Condition Check in Juniper Networks Junos OS on EX4k and QFX5k Series Platforms
CVE-2026-21910

7.1HIGH

Key Information:

Vendor

Juniper Networks
Status
Junos Os
Vendor
CVE Published:
15 January 2026

Badges

👾 Exploit Exists

What is CVE-2026-21910?

A vulnerability in the packet forwarding engine of Juniper Networks Junos OS on EX4k and QFX5k Series platforms permits unauthenticated network-adjacent attackers to exploit link flapping in an EVPN-VXLAN configuration. This exploitation can lead to the dropping of inter-VNI traffic when multiple load-balanced next-hop routes are in play, resulting in a Denial of Service (DoS). To recover services, affected devices must be restarted via specific commands. Affected systems include various models which require timely updates for protections against this issue.

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Affected Version(s)

Junos OS EX4k Series 0 < 21.4R3-S12

Junos OS EX4k Series 22.2 < 22.2*

Junos OS EX4k Series 22.4 < 22.4R3-S8

References

https://supportportal.juniper.net/JSA106009
vendor-advisory
https://kb.juniper.net/JSA106009
vendor-advisory

CVSS V4

Score:
7.1
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Adjacent Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

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