Medium [CVE-2026-21910] Junos: Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks…
This medium-severity Juniper Networks advisory covers CVE-2026-21910 affecting Junos, Junos OS, EX.
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Summary
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
- all versions before 21.4R3-S12,
- from 23.2 before 23.2R2-S5,
- from 23.4 before 23.4R2-S5,
Affected products named by the advisory: EX.
- 22.4
- 23.2
- 23.4
- 24.2
- 24.4
- all versions
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 21.4R3-S12
- 22.4R3-S8
- 23.2R2-S5
- 23.4R2-S5
- 24.2R2-S3
- 24.4R2
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S5, 24.2R2-S3, 24.4R2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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