FKIE_CVE-2021-27137
Vulnerability from fkie_nvd - Published: 2026-07-16 18:16 - Updated: 2026-07-22 05:17
Severity
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
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "DD-WRT",
"vendor": "DD-WRT",
"versions": [
{
"lessThan": "45724",
"status": "affected",
"version": "0",
"versionType": "custom"
}
]
}
],
"source": "cve@mitre.org"
}
],
"cisaActionDue": "2026-07-24",
"cisaExploitAdd": "2026-07-21",
"cisaRequiredAction": "Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA\u2019s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA\u2019s \u201cForensics Triage Requirements\u201d (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\u0027s internet exposure and ensuring adherence to BOD 26-04 patching guidelines.",
"cisaVulnerabilityName": "DD-WRT Stack-Based Buffer Overflow Vulnerability",
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:dd-wrt:dd-wrt:*:*:*:*:*:*:*:*",
"matchCriteriaId": "69D9E341-F731-4BA7-9410-8EEBA216CBCA",
"versionEndExcluding": "45724",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"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": "2026-07-22T05:17:07.330",
"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": "active"
},
{
"automatable": "no"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-07-21T00:00:00+00:00",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-16T18:16:39.113",
"references": [
{
"source": "cve@mitre.org",
"tags": [
"Exploit",
"Third Party Advisory"
],
"url": "https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html"
},
{
"source": "cve@mitre.org",
"tags": [
"Exploit",
"Third Party Advisory"
],
"url": "https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/"
},
{
"source": "cve@mitre.org",
"tags": [
"Patch"
],
"url": "https://svn.dd-wrt.com/changeset/45724"
},
{
"source": "cve@mitre.org",
"tags": [
"Exploit",
"Third Party Advisory"
],
"url": "https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/"
},
{
"source": "cve@mitre.org",
"tags": [
"Exploit"
],
"url": "https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"Exploit",
"Third Party Advisory"
],
"url": "https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"US Government Resource"
],
"url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137"
}
],
"sourceIdentifier": "cve@mitre.org",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-121"
}
],
"source": "cve@mitre.org",
"type": "Secondary"
}
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
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.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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