CVE-2021-27137NVD

Vulnerability Summary

An issue was discovered in router/upnp/src/ssdp.c in DD-WRT before 45724. An unsafe strcpy in the UPnP handling functionality allows an unauthenticated remote attacker to send a request that would overflow an internal fixed buffer. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request).

Severity Level

HIGH(8.1)

Published Date

Jul 16, 2026

Last Modified

Jul 22, 2026

Exploitation Status

ACTIVE

EPSS Score (30-Day)

16.49%Probability

Root Weakness (CWE)

CWE-121: Unknown/Unlisted Weakness ↗

Refer to the official MITRE database for detailed architectural specifications regarding this weakness.

CVSS v3.1 Base Metrics — Score 8.1 (HIGH)

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

Affected & Patched Versions

Affected Versions

Dd-wrt Dd-wrt < 45724

Patched Versions

Dd-wrt Dd-wrt 45724

🎁7-Day Free Trial — Try Pro or Team, no card required.

📧Email Delivery — Threat intel straight to your inbox.

♾️Unlimited Vendors — Track your entire stack.

🚨All New CVEs — Be the first to know.

📈EPSS Spike Alerts — Catch rising risk before it peaks.

🎯Custom EPSS/CVSS — Filter noise, focus on risk.

🛡️Exploit Intel — A 2nd confirmed-exploit signal beyond KEV.

🐙GitHub Issues — Auto-tracked, no duplicates.

📬Weekly Digest — One clean summary, not inbox spam.

🏷️Watchlist Groups — Tag alerts by team (Infra/AppSec/SOC).

💬Webhooks — Slack & Teams integration.

🔀Smart Routing — Critical alerts to one channel, rest to another.

🚫Ad-Free — Uninterrupted experience.