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

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).

8.1 HIGHEPSS 3.99%⚡ Known Exploited (CISA KEV)NVD: Analyzed

Last updated: 2026-07-22 05:17 UTC

Overview Affected Products References

NVD CVE.org

Overview

Severity

Score	Severity	Version	Vector String
8.1	HIGH	3.1mitre (CNA)	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CISA required action

⚡ Known exploited · remediation due Jul 24, 2026

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.

Details

CVE ID: CVE-2021-27137
Status: Analyzed
Assigner (CNA): mitre
Published: Jul 16, 2026
Last modified: 2026-07-22 05:17 UTC
Weaknesses: CWE-121 · Stack-based Buffer Overflow

Sources

Refreshed hourly from the sources above. Last fetched 2026-11-07 14:11 UTC.