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CVE-2026-67277

Status: AnalyzedHigh (8.8)⚠ Active exploitation

RouterOS accepts a "related" btest connection before the corresponding primary session has completed authentication. An unauthenticated client can use this state to start an IPv4 UDP test. With "random-data=false", the sender transmits an uninitialized tail from a kernel packet buffer. A separate unchecked, inverted packet-size interval causes unsigned integer underflow, anomalously large fragmented output, and can restart the RouterOS kernel.

This issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

CISA KEV — actively exploited

Affected technologies (1)

Mikrotik — Routeros

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-67277",
  "cveTags": [],
  "metrics": {
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          "role": "CISA Coordinator",
          "options": [
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              "exploitation": "active"
            },
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              "automatable": "yes"
            },
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              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-08T00:00:00+00:00"
        }
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    "cvssMetricV31": [
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        "source": "nvd@nist.gov",
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          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 4.2,
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    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "cvd@cert.pl",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
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          "Automatable": "NOT_DEFINED",
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          "valueDensity": "NOT_DEFINED",
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          "vulnIntegrityImpact": "NONE",
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          "modifiedAttackVector": "NOT_DEFINED",
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          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
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          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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  },
  "affected": [
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      "affectedData": [
        {
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          "product": "RouterOS",
          "versions": [
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              "version": "7.24",
              "lessThan": "7.24.2",
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  ],
  "published": "2026-09-05T20:17:18.120",
  "references": [
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      "url": "https://cert.pl/en/posts/2026/09/mikrotik-routeros-cve",
      "tags": [
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      ],
      "source": "cvd@cert.pl"
    },
    {
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      "source": "cvd@cert.pl"
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      "url": "https://forum.mikrotik.com/t/7-23-4-long-term-is-released/272801",
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      "source": "cvd@cert.pl"
    },
    {
      "url": "https://forum.mikrotik.com/t/7-24-2-stable-is-released/272800",
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      "source": "cvd@cert.pl"
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      "url": "https://npratley.net/reversing-mikrotiks-silent-patch-the-routeros-7-23-4-fix-they-wouldnt-explain/",
      "tags": [
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        "Third Party Advisory"
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      "source": "cvd@cert.pl"
    },
    {
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-67277",
      "tags": [
        "US Government Resource"
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "cvd@cert.pl",
      "description": [
        {
          "lang": "en",
          "value": "CWE-306"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "RouterOS accepts a \"related\" btest connection before the corresponding primary session has completed authentication. An unauthenticated client can use this state to start an IPv4 UDP test. With \"random-data=false\", the sender transmits an uninitialized tail from a kernel packet buffer. A separate unchecked, inverted packet-size interval causes unsigned integer underflow, anomalously large fragmented output, and can restart the RouterOS kernel.\n\n\n\nThis issue was fixed in versions: 6.49.21 (Long-term), 7.23.4 (Long-term) and 7.24.2 (Stable)"
    }
  ],
  "lastModified": "2026-09-11T12:52:29.533",
  "cisaActionDue": "2026-09-13",
  "cisaExploitAdd": "2026-09-10",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
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          "operator": "OR"
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  "sourceIdentifier": "cvd@cert.pl",
  "cisaRequiredAction": "Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.",
  "cisaVulnerabilityName": "MikroTik RouterOS Missing Authentication for Critical Function Vulnerability"
}