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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.

PUBLISHED Reserved 2026-01-05 | Published 2026-01-15 | Updated 2026-01-15 | Assigner juniper




MEDIUM: 6.5CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

HIGH: 7.1CVSS: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:Green

Problem types

CWE-754 Improper Check for Unusual or Exceptional Conditions

Product status

Default status
unaffected

Any version before 21.4R3-S12
affected

22.2 (semver) before 22.2*
affected

22.4 (semver) before 22.4R3-S8
affected

23.2 (semver) before 23.2R2-S5
affected

23.4 (semver) before 23.4R2-S5
affected

24.2 (semver) before 24.2R2-S3
affected

24.4 (semver) before 24.4R2
affected

References

supportportal.juniper.net/JSA106009 vendor-advisory

kb.juniper.net/JSA106009 vendor-advisory

cve.org (CVE-2026-21910)

nvd.nist.gov (CVE-2026-21910)

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