FKIE_CVE-2021-27137

Vulnerability from fkie_nvd - Published: 2026-07-16 18:16 - Updated: 2026-07-16 19:16
Severity
8.1 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in the UPnP handling functionality allows an unauthenticated remote attacker to send a request that would overflow an internal fixed buffer. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request).
References
cve@mitre.orghttps://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html
cve@mitre.orghttps://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
cve@mitre.orghttps://svn.dd-wrt.com/changeset/45724
cve@mitre.orghttps://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/
cve@mitre.orghttps://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo
134c704f-9b21-4f2e-91b3-4a467353bcc0https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "DD-WRT",
          "vendor": "DD-WRT",
          "versions": [
            {
              "lessThan": "45724",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "cve@mitre.org"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in the UPnP handling functionality allows an unauthenticated remote attacker to send a request that would overflow an internal fixed buffer. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request)."
    }
  ],
  "id": "CVE-2021-27137",
  "lastModified": "2026-07-16T19:16:43.080",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.1,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 5.9,
        "source": "cve@mitre.org",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2021-27137",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-16T18:24:17.054985Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-16T18:16:39.113",
  "references": [
    {
      "source": "cve@mitre.org",
      "url": "https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html"
    },
    {
      "source": "cve@mitre.org",
      "url": "https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/"
    },
    {
      "source": "cve@mitre.org",
      "url": "https://svn.dd-wrt.com/changeset/45724"
    },
    {
      "source": "cve@mitre.org",
      "url": "https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/"
    },
    {
      "source": "cve@mitre.org",
      "url": "https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/"
    }
  ],
  "sourceIdentifier": "cve@mitre.org",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-121"
        }
      ],
      "source": "cve@mitre.org",
      "type": "Secondary"
    }
  ]
}



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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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