CVE-2026-21912 (GCVE-0-2026-21912)

Vulnerability from cvelistv5 – Published: 2026-01-15 20:24 – Updated: 2026-01-15 20:50
VLAI?
Title
Junos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 line card reset
Summary
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset. On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:  * all versions before 21.2R3-S10,  * from 21.4 before 21.4R3-S9,  * from 22.2 before 22.2R3-S7,  * from 22.4 before 22.4R3-S6,  * from 23.2 before 23.2R2-S2,  * from 23.4 before 23.4R2-S3,  * from 24.2 before 24.2R2.
Severity ?
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8 (Medium)
CVSS:4.0/AV:L/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/U:Amber
CWE
  • CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 0 , < 21.2R3-S10 (semver)
Affected: 21.4 , < 21.4R3-S9 (semver)
Affected: 22.2 , < 22.2R3-S7 (semver)
Affected: 22.4 , < 22.4R3-S6 (semver)
Affected: 23.2 , < 23.2R2-S2 (semver)
Affected: 23.4 , < 23.4R2-S3 (semver)
Affected: 24.2 , < 24.2R2 (semver)
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repeated execution of the \u0027show system firmware\u0027 CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:\\u00a0\\n\\n\\n\\n  *  all versions before 21.2R3-S10,\\u00a0\\n  *  from 21.4 before 21.4R3-S9,\\u00a0\\n  *  from 22.2 before 22.2R3-S7,\\u00a0\\n  *  from 22.4 before 22.4R3-S6,\\u00a0\\n  *  from 23.2 before 23.2R2-S2,\\u00a0\\n  *  from 23.4 before 23.4R2-S3,\\u00a0\\n  *  from 24.2 before 24.2R2.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"\u003cspan style=\\\"background-color: rgb(255, 255, 255);\\\"\u003eA Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics\u0026nbsp;of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the \u0027show system firmware\u0027 CLI command to cause an LC480 or LC2101 line card to reset.\u003cbr\u003e\u003c/span\u003e\u003cbr\u003eOn MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the \u0027show system firmware\u0027 CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.\u003cp\u003eThis issue affects Junos OS on MX10k Series:\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003eall versions before 21.2R3-S10,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 21.4 before 21.4R3-S9,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 22.2 before 22.2R3-S7,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 22.4 before 22.4R3-S6,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.2 before 23.2R2-S2,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 23.4 before 23.4R2-S3,\u0026nbsp;\u003c/li\u003e\u003cli\u003efrom 24.2 before 24.2R2.\u003c/li\u003e\u003c/ul\u003e\u003cp\u003e\u003c/p\u003e\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-367\", \"description\": \"CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition\"}]}], \"providerMetadata\": {\"orgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"shortName\": \"juniper\", \"dateUpdated\": \"2026-01-15T20:24:20.087Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21912\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-15T20:50:28.949Z\", \"dateReserved\": \"2026-01-05T17:32:48.710Z\", \"assignerOrgId\": \"8cbe9d5a-a066-4c94-8978-4b15efeae968\", \"datePublished\": \"2026-01-15T20:24:20.087Z\", \"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.