CVE-2021-27137
DD-WRT Stack-Based Buffer Overflow Vulnerability
Exploited in the wild
This vulnerability is on the CISA Known Exploited Vulnerabilities list, added 2026-07-21. Federal due date: 2026-07-24.
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.
Impact
DD-WRT contains a stack-based buffer overflow vulnerability that could allow an unauthenticated attacker to overflow an internal buffer used by UPnP and trigger a code execution vulnerability.
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Dd-Wrt | Dd-Wrt | before 45724 |
Weakness classification
References
- NVD record
- CVE.org record
- CISA KEV catalog
- https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html
- https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
- https://svn.dd-wrt.com/changeset/45724
- 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