CVE-2026-21903 (GCVE-0-2026-21903)

Vulnerability from cvelistv5 – Published: 2026-01-15 20:18 – Updated: 2026-01-15 21:12
VLAI?
Title
Junos OS: Subscribing to telemetry sensors at scale causes all FPCs to crash
Summary
A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker, authenticated with low privileges to cause a Denial-of-Service (DoS). Subscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart. The issue was not seen when YANG packages for the specific sensors were installed. This issue affects Junos OS:  * all versions before 22.4R3-S7, * 23.2 version before 23.2R2-S4, * 23.4 versions before 23.4R2.
Severity ?
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.1 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
CWE
  • CWE-121 - Stack-based Buffer Overflow
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 0 , < 22.4R3-S7 (semver)
Affected: 23.2 , < 23.2R2-S4 (semver)
Affected: 23.4 , < 23.4R2 (semver)
Create a notification for this product.
Date Public ?
2026-01-14 17:00
Show details on NVD website
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22.4R3-S7, 23.2R2-S4, 23.4R2, 24.2R1, and all subsequent releases.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"The following software releases have been updated to resolve this specific issue: 22.4R3-S7, 23.2R2-S4, 23.4R2, 24.2R1, and all subsequent releases.\", \"base64\": false}]}], \"datePublic\": \"2026-01-14T17:00:00.000Z\", \"references\": [{\"url\": \"https://supportportal.juniper.net/JSA106022\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://kb.juniper.net/JSA106022\", \"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\": \"A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker,\\u00a0authenticated\\u00a0with low privileges to cause a Denial-of-Service (DoS).\\n\\n\\n\\nSubscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart.\\nThe issue was not seen when YANG packages for the specific sensors were installed. \\n\\n\\n\\nThis issue affects Junos OS:\\u00a0\\n\\n\\n\\n  *  all versions before 22.4R3-S7,\\n  *  23.2 version before 23.2R2-S4,\\n  *  23.4 versions before 23.4R2.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"A Stack-based Buffer Overflow vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS allows a network-based attacker,\u0026nbsp;\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eauthenticated\u003c/span\u003e\u0026nbsp;with low privileges to cause a Denial-of-Service (DoS).\u003cbr\u003e\u003cbr\u003e\\n\\n\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eSubscribing to telemetry sensors at scale causes all FPC connections to drop, resulting in an FPC crash and restart.\u003cbr\u003eThe issue was not seen when YANG packages for the specific sensors were installed. \u003c/span\u003e\\n\\n\u003cbr\u003e\u003cbr\u003e\u003cp\u003eThis issue affects Junos OS:\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003eall versions before 22.4R3-S7,\u003c/li\u003e\u003cli\u003e23.2 version before 23.2R2-S4,\u003c/li\u003e\u003cli\u003e23.4 versions before 23.4R2.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-121\", \"description\": \"CWE-121 Stack-based Buffer Overflow\"}]}], \"configurations\": [{\"lang\": \"en\", \"value\": \"A device is only exposed to this issue if GRPC services are configured:\\n\\n[ system services extension-service request-response grpc ]\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"A device is only exposed to this issue if GRPC services are configured:\u003cbr\u003e\u003cbr\u003e\u003ctt\u003e[ system services extension-service request-response grpc ]\u003c/tt\u003e\", \"base64\": false}]}], \"providerMetadata\": {\"orgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"shortName\": \"juniper\", \"dateUpdated\": \"2026-01-15T20:18:36.767Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21903\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-15T21:12:08.631Z\", \"dateReserved\": \"2026-01-05T17:32:48.709Z\", \"assignerOrgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"datePublished\": \"2026-01-15T20:18:36.767Z\", \"assignerShortName\": \"juniper\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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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.



Detection rules are retrieved from Rulezet.