CVE-2026-21910 (GCVE-0-2026-21910)

Vulnerability from cvelistv5 – Published: 2026-01-15 20:23 – Updated: 2026-01-15 20:51
VLAI?
Title
Junos OS: EX4k Series, QFX5k Series: In an EVPN-VXLAN configuration link flaps cause Inter-VNI traffic drop
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.
Severity ?
6.5 (Medium)
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.1 (High)
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/AU:Y/R:U/RE:M/U:Green
CWE
  • CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 0 , < 21.4R3-S12 (semver)
Affected: 22.2 , < 22.2* (semver)
Affected: 22.4 , < 22.4R3-S8 (semver)
Affected: 23.2 , < 23.2R2-S5 (semver)
Affected: 23.4 , < 23.4R2-S5 (semver)
Affected: 24.2 , < 24.2R2-S3 (semver)
Affected: 24.4 , < 24.4R2 (semver)
Create a notification for this product.
Date Public ?
2026-01-14 17:00
Show details on NVD website
To clipboard 

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Advisory\"]},{\"url\":\"https://supportportal.juniper.net/JSA106009\",\"source\":\"sirt@juniper.net\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-21910\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-01-15T20:51:52.841479Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-01-15T20:51:54.771Z\"}}], \"cna\": {\"title\": \"Junos OS: EX4k Series, QFX5k Series: In an EVPN-VXLAN configuration link flaps cause Inter-VNI traffic drop\", \"source\": {\"defect\": [\"1847849\"], \"advisory\": \"JSA106009\", \"discovery\": \"USER\"}, \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 6.5, \"attackVector\": \"ADJACENT_NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}, {\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"USER\", \"baseScore\": 7.1, \"Automatable\": \"YES\", \"attackVector\": \"ADJACENT\", \"baseSeverity\": \"HIGH\", \"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/AU:Y/R:U/RE:M/U:Green\", \"providerUrgency\": \"GREEN\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"subAvailabilityImpact\": \"LOW\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"MODERATE\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"Juniper Networks\", \"product\": \"Junos OS\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"21.4R3-S12\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"22.2\", \"lessThan\": \"22.2*\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"22.4\", \"lessThan\": \"22.4R3-S8\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"23.2\", \"lessThan\": \"23.2R2-S5\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"23.4\", \"lessThan\": \"23.4R2-S5\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"24.2\", \"lessThan\": \"24.2R2-S3\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"24.4\", \"lessThan\": \"24.4R2\", \"versionType\": \"semver\"}], \"platforms\": [\"EX4k Series\", \"QFX5k Series\"], \"defaultStatus\": \"unaffected\"}], \"exploits\": [{\"lang\": \"en\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Juniper SIRT is not aware of any malicious exploitation of this vulnerability.\", \"base64\": false}]}], \"solutions\": [{\"lang\": \"en\", \"value\": \"The following software releases have been updated to resolve this specific issue: Junos OS 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S5, 24.2R2-S3, 24.4R2, 25.2R1, and all subsequent releases.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"The following software releases have been updated to resolve this specific issue: Junos OS 21.4R3-S12, 22.4R3-S8, 23.2R2-S5, 23.4R2-S5, 24.2R2-S3, 24.4R2, 25.2R1, and all subsequent releases.\", \"base64\": false}]}], \"datePublic\": \"2026-01-14T17:00:00.000Z\", \"references\": [{\"url\": \"https://supportportal.juniper.net/JSA106009\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://kb.juniper.net/JSA106009\", \"tags\": [\"vendor-advisory\"]}], \"workarounds\": [{\"lang\": \"en\", \"value\": \"There are no known workarounds for this issue.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"There are no known workarounds for this issue.\", \"base64\": false}]}], \"x_generator\": {\"engine\": \"Vulnogram 0.1.0-dev\"}, \"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.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003e\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eAn 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\u0026nbsp;flapping an interface to cause traffic between VXLAN Network Identifiers (VNIs) to drop, leading to a Denial of Service (DoS).\u003c/span\u003e\u003cbr\u003e\u003c/span\u003e\u003cbr\u003eOn 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.\u003cbr\u003e\u003cbr\u003eThis issue is only applicable to\u0026nbsp;systems that support EVPN-VXLAN Virtual Port-Link Aggregation Groups (VPLAG), such as the QFX5110, QFX5120, QFX5200, EX4100, EX4300, EX4400, and EX4650.\u003cbr\u003e\u003cbr\u003eService can only be restored by restarting the affected FPC via the \u0027\u003ctt\u003erequest chassis fpc restart slot \u0026lt;slot-number\u0026gt;\u003c/tt\u003e\u0027 command.\u003cbr\u003e\u003cbr\u003e\u003cp\u003eThis issue affects Junos OS \\n\\non EX4k and QFX5k Series:\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003eall versions before 21.4R3-S12,\u0026nbsp;\u003c/li\u003e\u003cli\u003eall versions of 22.2\u003c/li\u003e\u003cli\u003efrom 22.4 before 22.4R3-S8,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.2 before 23.2R2-S5,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.4 before 23.4R2-S5,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 24.2 before 24.2R2-S3,\u003c/li\u003e\u003cli\u003efrom 24.4 before 24.4R2.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003e\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-754\", \"description\": \"CWE-754 Improper Check for Unusual or Exceptional Conditions\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"This issue requires the following configuration:\\n\\n\\n\\n[interfaces \u003cif\u003e ether-options 802.3ad ae0]\\n[interfaces ae0 aggregated-ether-options lacp]\\n\\n[protocols bgp group \u003cname\u003e family evpn signaling]\\n[protocols evpn encapsulation vxlan]\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"This issue requires the following configuration:\u003cbr\u003e\u003cbr\u003e\\n\\n\u003ctt\u003e\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003e[interfaces \u0026lt;if\u0026gt; ether-options 802.3ad ae0]\u003c/span\u003e\u003cbr\u003e[interfaces ae0 aggregated-ether-options lacp]\u003cbr\u003e\u003c/tt\u003e\u003cbr\u003e\u003ctt\u003e\u003ctt\u003e[protocols bgp group \u0026lt;name\u0026gt; family evpn signaling]\u003cbr\u003e\u003c/tt\u003e[protocols evpn encapsulation vxlan]\u003c/tt\u003e\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"shortName\": \"juniper\", \"dateUpdated\": \"2026-01-15T20:23:29.682Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21910\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-15T20:51:57.933Z\", \"dateReserved\": \"2026-01-05T17:32:48.710Z\", \"assignerOrgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"datePublished\": \"2026-01-15T20:23:29.682Z\", \"assignerShortName\": \"juniper\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

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.



Detection rules are retrieved from Rulezet.