FKIE_CVE-2026-21910
Vulnerability from fkie_nvd - Published: 2026-01-15 21:16 - Updated: 2026-01-16 15:55
Severity ?
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 <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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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\u00a0flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).\n\nOn all EX4k and QFX5k platforms, a link flap in an\n\nEVPN-VXLAN configuration Link Aggregation Group (LAG)\nresults in Inter-VNI traffic dropping when there are multiple load-balanced next-hop routes for the same destination.\n\nThis issue is only applicable to\u00a0systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.\n\nService can only be restored by restarting the affected FPC via the \u0027request chassis fpc restart slot \u003cslot-number\u003e\u0027 command.\n\nThis issue affects Junos OS \n\non EX4k and QFX5k Series:\u00a0\n\n\n\n * all versions before 21.4R3-S12,\u00a0\n * all versions of 22.2\n * from 22.4 before 22.4R3-S8,\u00a0\n * from 23.2 before 23.2R2-S5,\u00a0\n * from 23.4 before 23.4R2-S5,\u00a0\n * from 24.2 before 24.2R2-S3,\n * from 24.4 before 24.4R2."
}
],
"id": "CVE-2026-21910",
"lastModified": "2026-01-16T15:55:12.257",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "ADJACENT_NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 6.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 2.8,
"impactScore": 3.6,
"source": "sirt@juniper.net",
"type": "Primary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "YES",
"Recovery": "USER",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "NONE",
"attackVector": "ADJACENT",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 7.1,
"baseSeverity": "HIGH",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "GREEN",
"subAvailabilityImpact": "LOW",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:U/V:X/RE:M/U:Green",
"version": "4.0",
"vulnAvailabilityImpact": "HIGH",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE",
"vulnerabilityResponseEffort": "MODERATE"
},
"source": "sirt@juniper.net",
"type": "Secondary"
}
]
},
"published": "2026-01-15T21:16:06.920",
"references": [
{
"source": "sirt@juniper.net",
"url": "https://kb.juniper.net/JSA106009"
},
{
"source": "sirt@juniper.net",
"url": "https://supportportal.juniper.net/JSA106009"
}
],
"sourceIdentifier": "sirt@juniper.net",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-754"
}
],
"source": "sirt@juniper.net",
"type": "Primary"
}
]
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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