{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2021-0243",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-0243",
    "idYear": 2021,
    "status": "PUBLISHED",
    "publishedAt": "2021-04-22T19:37:08.073Z",
    "updatedAt": "2024-09-17T00:51:52.928Z",
    "importedAt": "2026-10-24T01:56:21.187Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "Junos OS: EX4300: Stateless firewall policer fails to discard traffic",
      "summary": "Improper Handling of Unexpected Data in the firewall policer of Juniper Networks Junos OS on EX4300 switches allows matching traffic to exceed set policer limits, possibly leading to a limited Denial of Service (DoS) condition. When the firewall policer discard action fails on a Layer 2 port, it will allow traffic to pass even though it exceeds set policer limits. Traffic will not get discarded, and will be forwarded even though a policer discard action is configured. When the issue occurs, traffic is not discarded as desired, which can be observed by comparing the Input bytes with the Output bytes using the following command: user@junos> monitor interface traffic Interface Link Input bytes (bps) Output bytes (bps) ge-0/0/0 Up 37425422 (82616) 37425354 (82616) <<<< egress ge-0/0/1 Up 37425898 (82616) 37425354 (82616) <<<< ingress The expected output, with input and output counters differing, is shown below: Interface Link Input bytes (bps) Output bytes (bps) ge-0/0/0 Up 342420570 (54600) 342422760 (54600) <<<< egress ge-0/0/1 Up 517672120 (84000) 342420570 (54600) <<<< ingress This issue only affects IPv4 policing. IPv6 traffic and firewall policing actions are not affected by this issue. This issue affects Juniper Networks Junos OS on the EX4300: All versions prior to 17.3R3-S10; 17.4 versions prior to 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R3-S6; 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R3-S6; 19.1 versions prior to 19.1R3-S3; 19.2 versions prior to 19.2R3-S1; 19.3 versions prior to 19.3R3-S1; 19.4 versions prior to 19.4R3; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2.",
      "affected": [
        {
          "vendor": "Juniper Networks",
          "product": "Junos OS",
          "platforms": [
            "EX4300"
          ],
          "versions": [
            {
              "version": "unspecified",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "17.3R3-S10"
            },
            {
              "version": "17.4",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "17.4R3-S3"
            },
            {
              "version": "18.1",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "18.1R3-S11"
            },
            {
              "version": "18.2",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "18.2R3-S6"
            },
            {
              "version": "18.3",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "18.3R3-S4"
            },
            {
              "version": "18.4",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "18.4R3-S6"
            },
            {
              "version": "19.1",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "19.1R3-S3"
            },
            {
              "version": "19.2",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "19.2R3-S1"
            },
            {
              "version": "19.3",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "19.3R3-S1"
            },
            {
              "version": "19.4",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "19.4R3"
            },
            {
              "version": "20.1",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "20.1R2"
            },
            {
              "version": "20.2",
              "status": "affected",
              "versionType": "custom",
              "lessThan": "20.2R2"
            }
          ]
        }
      ]
    }
  }
}