CISA_KEV · JULY 2026 · EARLY WARNING

DD-WRT Buffer Overflow Vulnerability Under Investigation

EARLY WARNING · UNCONFIRMED. This page describes a developing threat that 0Day surfaced from early signals and has not yet independently confirmed. Details may change. Always verify against the primary sources before acting.
CVE-2021-27137Severity: HIGH

An early warning has been issued regarding a stack-based buffer overflow vulnerability in DD-WRT that could allow unauthenticated attackers to execute code.

What happened

An early warning has been issued regarding a vulnerability tracked as CVE-2021-27137 in DD-WRT. This vulnerability reportedly allows an unauthenticated attacker to overflow an internal buffer used by UPnP, potentially triggering a code execution vulnerability. The issue is under investigation and has been added to CISA's Known Exploited Vulnerabilities Catalog. Professional software engineers using DD-WRT are advised to upgrade to the latest version and review UPnP settings to minimize exposure. Further details about the vulnerability and affected versions should be obtained from primary sources as the situation develops.

How 0Day mitigates this

MATCHED TO YOUR ACTUAL DEPENDENCY GRAPH0Day matches every incoming threat signal against your GitHub organization’s full dependency graph, including transitive dependencies. If dd-wrt is anywhere in your dependency tree, the engineers who own the affected repositories get a push alert the moment it is flagged — no manual audit to remember to run.

Read how this differs from waiting on a scanner to catch a known advisory, or see the exact, read-only access 0Day needs to do this for an organization.

Join the 0Day waitlist →

← Back to all threats