CVE-2021-27137

Published: Jul 16, 2026Modified: Jul 22, 2026CISA KEV

8.1

Vector

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

Exploitability: 2.2 / Impact: 5.9

Source: MITRE (Secondary)

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).

Affected (1)

Products: Dd Wrt: Dd Wrt

1 product

Configuration A

1 vulnerable

Vulnerable Software	Affected Versions
Dd Wrt Dd Wrt	Before 45724

Related CWEs

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).

References (7)

https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html

Source: cve@mitre.org

ExploitThird Party Advisory

https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/

Source: cve@mitre.org

ExploitThird Party Advisory

https://svn.dd-wrt.com/changeset/45724

Source: cve@mitre.org

Patch

https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/

Source: cve@mitre.org

ExploitThird Party Advisory

https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo

Source: cve@mitre.org

Exploit

https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

ExploitThird Party Advisory

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137

Source: 134c704f-9b21-4f2e-91b3-4a467353bcc0

US Government Resource

Timeline

No history available yet.