Riskcovery

CVE-2026-21910

Junos OS: EX4k Series, QFX5k Series: In an EVPN-VXLAN configuration link flaps cause Inter-VNI traffic drop

State
Published
Severity
7.1 High
Published
Jan 15, 2026
Updated
Jan 15, 2026
Reserved
Jan 5, 2026

Read the record on cve.org

Description

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 an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).

On all EX4k and QFX5k platforms, a link flap in an

EVPN-VXLAN configuration Link Aggregation Group (LAG) results in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.

This issue is only applicable to systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.

Service can only be restored by restarting the affected FPC via the 'request chassis fpc restart slot <slot-number>' command.

This issue affects Junos OS

on EX4k and QFX5k Series:

* all versions before 21.4R3-S12,  * all versions of 22.2 * from 22.4 before 22.4R3-S8,  * from 23.2 before 23.2R2-S5,  * from 23.4 before 23.4R2-S5,  * from 24.2 before 24.2R2-S3, * from 24.4 before 24.4R2.

Scores

CVSSScoreVectorSource
4.07.1 HighCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M/U:Greenjuniper
3.16.5 MediumCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hjuniper

Weaknesses

  • CWE-754 Improper Check for Unusual or Exceptional Conditions

Affected Products

ProductVersions
Junos OSJuniper Networks
  • before 21.4R3-S12Affected
  • 22.2 to before 22.2*Affected
  • 22.4 to before 22.4R3-S8Affected
  • 23.2 to before 23.2R2-S5Affected
  • 23.4 to before 23.4R2-S5Affected
  • 24.2 to before 24.2R2-S3Affected
  • 24.4 to before 24.4R2Affected

References

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