CVE-2021-27137

Published Jul 16, 2026

Last updated a month ago

Exploit knownCVSS high 8.1
Ubuntu
Network
Open source
IoT

Overview

Description
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).
Source
cve@mitre.org
NVD status
Analyzed
Products
dd-wrt

Risk scores

CVSS 3.1

Type
Secondary
Base score
8.1
Impact score
5.9
Exploitability score
2.2
Vector string
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Known exploits

Data from CISA

Vulnerability name
DD-WRT Stack-Based Buffer Overflow Vulnerability
Exploit added on
Jul 21, 2026
Exploit action due
Jul 24, 2026
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.

Weaknesses

cve@mitre.org
CWE-121

Social media

Hype score
Not currently trending

  1. 米国サイバーセキュリティ・社会基盤安全保障庁(CISA)が既知の悪用された脆弱性カタログに4件の脆弱性を追加。DD-WRTのCVE-2021-27137、LangflowのCVE-2026-0770、WordPressのCVE-2026-63030とCVE-2026-60137。対処期限は前3件が3日

    @__kokumoto

    21 Jul 2026

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  2. 🚨 4 new CISA KEV adds today CVE-2021-27137, CVE-2026-0770, CVE-2026-63030, CVE-2026-60137 https://t.co/0StDFCzdCI #boarnet #cybersecurity #cisakev #cve #threatintelligence #malware

    @boarnetio

    21 Jul 2026

    29 Impressions

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Configurations

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References

Sources include official advisories and independent security research.