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

In CISA’s Known Exploited Vulnerabilities catalog: DD-WRT Stack-Based Buffer Overflow Vulnerability.

Added 2026-07-21, federal remediation due 2026-07-24. Known ransomware use: Unknown.

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.