CVE-2021-27137

CVE Enrichment

CVSS: 8.1 HIGH
EPSS: 4.00%
EPSS Percentile: 90.29%
CISA KEV: YES — Known Exploited Vulnerability

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).

Technical Details

CVSS Version: 3.1
CNA / NVD Source: cve@mitre.org
Published: 17-Jul-2026 01:16
Last Modified: 22-Jul-2026 12:17
EPSS Date: 2026-10-12
CWE: CWE-121

CVSS Vector


            CVSS:3.1                            AV:N /
                            AC:H /
                            PR:N /
                            UI:N /
                            S:U /
                            C:H /
                            I:H /
                            A:H

CISA KEV Details

Date Added: 2026-07-21
Remediation Due: 2026-07-24
Known Ransomware Campaign Use: Unknown
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.
Notes: This vulnerability affects a common open-source component, third-party library, proprietary implementation, or a protocol used by different products. Please check with specific vendors for information on patching status. For more information, please see: https://svn.dd-wrt.com/changeset/45724 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2021-27137

Affected Products / Versions

dd-wrt / dd-wrt
Version / affected range: * · before (exclusive) 45724
cpe:2.3:o:dd-wrt:dd-wrt:*:*:*:*:*:*:*:*

References

Last enrichment sync: 13-Oct-2026 03:12
Sources: NVD · FIRST EPSS · CISA KEV
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Reported Context (2)

CVE (129)

Malware (10)

Threat Actors (14)

Vendors (42)

Products (120)

Tools (2)

Industries (2)

Countries (2)

Note: Related entities, including threat actors, malware, CVEs, MITRE ATT&CK techniques, vendors, products, tools, countries, and industries, are shown when they appear in the same reporting. Their presence does not necessarily mean they were targeted, compromised, vulnerable, responsible for the activity, or directly involved in the incident.