CVE-2021-27137: DD-WRT Stack-Based Buffer Overflow Vulnerability

Required action (CISA's text)

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.

Description (NVD)

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.

SOURCES

• CISA KEVCISA Known Exploited Vulnerabilities catalog

Data from NVD, CISA KEV, FIRST EPSS and vendor advisories. Updated 10 Nov 2026.