CVE-2021-27137

Analyzed
Published: 16 Jul 2026, 00:00
Last modified:22 Jul 2026, 03:55

Vulnerability Summary

Overall Risk (default)
medium
46/100
CVSS Score
8.1 HIGH
v3.1 (cve.org)
EPSS Score
16.49% MEDIUM
16% probability 0.00%
KEV
Listed
CISA
1 listing
Ransomware
No reports
Public exploits
4 found
Dark Web
Not detected

Timeline

16 Jul 2026, 00:00
Published
Vulnerability first disclosed
21 Jul 2026, 00:00
Added to CISA KEV
DD-WRT Stack-Based Buffer Overflow Vulnerability
22 Jul 2026, 03:55
Last Modified
Vulnerability information updated
24 Jul 2026, 00:00
CISA Remediation Due
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.

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).

CVSS Metrics

  • v3.1•HIGH•Score: 8.1CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 16.49%• Percentile: 97%

Techniques & Countermeasures

  • CWE-121•Stack-based Buffer Overflow

    A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Affected Systems

  • dd-wrt•dd-wrt

    < 45724

References (6)