CVE-2021-27137: DD-WRT Stack-Based Buffer Overflow Vulnerability
Affects DD-WRT DD-WRTSource CISA KEV
No CVSS score published yet
- Exploitation
Actively exploited – in CISA KEV since 07/21/2026
- KEV deadline
- 07/24/2026
- EPSS
- 4.0% chance of exploitation in 30 days – higher than 90% of CVEs
What to do
CISA required action
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.
- svn.dd-wrt.com/changeset/45724 (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2021-27137 (opens in a new tab)
Description
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.
Weaknesses
References
- svn.dd-wrt.com/changeset/45724 (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (opens in a new tab)
- cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2021-27137 (opens in a new tab)
- cisa.gov/known-exploited-vulnerabilities-catalog?search=CVE-2021-27137 (opens in a new tab)