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CVE-2026-77556

Status: DeferredHigh (7.5)—

A malicious actor with access to the network could exploit an Out-of-bounds Read vulnerability found in certain UniFi gateway devices to execute a Denial of Service (DoS) attack on the device.

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).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

AV:N sin privilegios indica T1190 (aplicación expuesta en red). CWE-125 (out-of-bounds read) y descripción de DoS remoto apunta a T1499.004 (flood de aplicación).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

UI — Unifi GatewayAI

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-77556",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77556",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-22T19:33:13.667722Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "fe490ce8-0395-4072-90d8-2707e1bdf984",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "fe490ce8-0395-4072-90d8-2707e1bdf984",
      "affectedData": [
        {
          "vendor": "Ubiquiti Inc",
          "product": "Dream Machines",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Enterprise Firewalls",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Dream Routers",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Cloud Gateways",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Dream Wall",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Express",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "4.0.21",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "Express 7",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.31",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        },
        {
          "vendor": "Ubiquiti Inc",
          "product": "UniFi Gateways",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "5.1.26",
              "versionType": "semver"
            }
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-09-22T19:16:51.860",
  "references": [
    {
      "url": "https://community.ui.com/releases/Security-Advisory-Bulletin-069-069/07e367a7-edec-4d85-a058-f97e5ce9ac9c",
      "source": "fe490ce8-0395-4072-90d8-2707e1bdf984"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "fe490ce8-0395-4072-90d8-2707e1bdf984",
      "description": [
        {
          "lang": "en",
          "value": "CWE-125"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A malicious actor with access to the network could exploit an Out-of-bounds Read vulnerability found in certain UniFi gateway devices to execute a Denial of Service (DoS) attack on the device."
    }
  ],
  "lastModified": "2026-09-22T20:17:08.570",
  "sourceIdentifier": "fe490ce8-0395-4072-90d8-2707e1bdf984"
}