All vulnerabilities
CVE-2021-27137

DD-WRT Stack-Based Buffer Overflow Vulnerability

DD-WRT DD-WRT
Open in ThreatlineRecord JSON
CVSS
8.1High
ExploitationExploited in the wildAdded to KEV 21 Jul 2026CISA KEV
Exploit odds (EPSS)4.00%Chance of exploitation activity in the next 30 days, higher than 90% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in45724Fixed versionCVE List
Federal deadline24 Jul 2026Remediation due date for US federal agenciesCISA KEV
CISA required actionApply 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. CISA KEV
Patching is not enoughCISA requires federal agencies to look for signs of compromise on affected systems, not only patch (forensic triage under BOD 26-04). Treat exposed systems as possibly compromised. CISA guidance

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Timeline

  1. 16 Jul 2026, 00:00 UTCPublishedCVE List
  2. 21 Jul 2026Added to CISA KEVCISA KEV

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.

Text from CVE List

Affected versions 1

  • DD-WRTaffected: all versions before 45724CVE List

References 7