---
cve: "CVE-2021-27137"
severity: "HIGH"
cvss: 8.1
epss: "16.5%"
vendor: "DD-WRT"
kev: true
exploited: true
published: "2026-07-16 18:16:39"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-12T08:09:15+02:00"
---

# CVE-2021-27137

> 8.1 HIGH · ⚠️ CISA KEV (53 Tage) · 🔓 Exploited

## Beschreibung

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).

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Referenzen

- <https://svn.dd-wrt.com/changeset/45724>
- <https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/>
- <https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html>
- <https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/>
- <https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo>
- <https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2021-27137) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_