CVE-2026-21921 (GCVE-0-2026-21921)

Vulnerability from cvelistv5 – Published: 2026-01-15 20:28 – Updated: 2026-01-15 20:55
VLAI
Title
Junos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash
Summary
A Use After Free vulnerability in the chassis daemon (chassisd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based attacker authenticated with low privileges to cause a Denial-of-Service (DoS). When telemetry collectors are frequently subscribing and unsubscribing to sensors continuously over a long period of time, telemetry-capable processes like chassisd, rpd or mib2d will crash and restart, which - depending on the process - can cause a complete outage until the system has recovered. This issue affects:  Junos OS:  * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2; Junos OS Evolved: * all versions before 22.4R3-S8-EVO, * 23.2 versions before 23.2R2-S5-EVO, * 23.4 versions before 23.4R2-EVO.
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/AU:Y/R:A/RE:M
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-01-15 20:54 UTC
CWE
Assigner
juniper CNA under the mitre root
CNA scorecard B 84/100 over 193 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Juniper Networks Junos OS Affected: 0 , < 22.4R3-S8 (semver)
Affected: 23.2 , < 23.2R2-S5 (semver)
Affected: 23.4 , < 23.4R2 (semver)
guessed Create a notification for this product.
Juniper Networks Junos OS Evolved Affected: 0 , < 22.4R3-S8-EVO (semver)
Affected: 23.2 , < 23.2R2-S5-EVO (semver)
Affected: 23.4 , < 23.4R2-EVO (semver)
guessed Create a notification for this product.
Date Public
2026-01-14 17:00
Show details on NVD website
To clipboard 

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              "value": "The following software releases have been updated to resolve this specific issue:\nJunos OS Evolved: 22.4R3-S8-EVO, 23.2R2-S5-EVO, 23.4R2-EVO, 24.2R1-EVO,\u00a0and all subsequent releases;\nJunos OS: 22.4R3-S8, 23.2R2-S5, 23.4R2, 24.2R1, and all subsequent releases."
            }
          ],
          "source": {
            "advisory": "JSA106021",
            "defect": [
              "1791928"
            ],
            "discovery": "INTERNAL"
          },
          "title": "Junos OS and Junos OS Evolved: When telemetry collectors are frequently subscribing and unsubscribing to sensors chassisd or rpd will crash",
          "workarounds": [
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              "supportingMedia": [
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                  "value": "There are no known workarounds for this issue."
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              "value": "There are no known workarounds for this issue."
            }
          ],
          "x_generator": {
            "engine": "Vulnogram 0.1.0-dev"
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      "cveMetadata": {
        "assignerOrgId": "8cbe9d5a-a066-4c94-8978-4b15efeae968",
        "assignerShortName": "juniper",
        "cveId": "CVE-2026-21921",
        "datePublished": "2026-01-15T20:28:29.656Z",
        "dateReserved": "2026-01-05T17:32:48.712Z",
        "dateUpdated": "2026-01-15T20:55:25.182Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
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    }
  }
}



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