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Medium severity6.5NVD Advisory· Published Jan 15, 2026· Updated Jun 17, 2026

CVE-2026-21910

CVE-2026-21910

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 ' 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.

Affected products

69
  • Juniper Networks/Junoscpe-rescue67 versions
    0+ 66 more
    • (no CPE)range: 0
    • cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*range: <21.4
    • cpe:2.3:o:juniper:junos:21.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s10:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s11:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s5:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s6:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s7:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s8:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:21.4:r3-s9:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.2:*:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s5:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s6:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:22.4:r3-s7:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.2:r2-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s3:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:23.4:r2-s4:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r2-s1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.2:r2-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:-:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s2:*:*:*:*:*:*
    • cpe:2.3:o:juniper:junos:24.4:r1-s3:*:*:*:*:*:*
    • (no CPE)range: <21.4R3-S12, 22.2, <22.4R3-S8, <23.2R2-S5, <23.4R2-S5, <24.2R2-S3, <24.4R2
  • Juniper Networks/QFX5k Seriesllm-fuzzy
    Range: <21.4R3-S12, 22.2, <22.4R3-S8, <23.2R2-S5, <23.4R2-S5, <24.2R2-S3, <24.4R2
  • Juniper Networks/EX4k Seriesllm-create
    Range: <21.4R3-S12, 22.2, <22.4R3-S8, <23.2R2-S5, <23.4R2-S5, <24.2R2-S3, <24.4R2

Patches

Vulnerability mechanics

References

2

News mentions

0

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