CVE-2021-27137 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-27137HIGH

DD-WRT DD-WRT

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   H   N   N  U  H  H  H    8.1   .1649   96.7   YES

AFFECTED
  Product  Versions     Fixed
  DD-WRT   unspecified  —

TIMELINE
  Feb 10  Reserved by mitre
  Jul 21  Added to CISA KEV, remediation due 2026-07-24
  Jul 21  Published (CNA: mitre)
  Jul 22  EXPLOIT PUBLISHED — CVE-2021-27137 (DD-WRT). Public exploit reference added.
  Jul 25  DUE DATE PASSED — CVE-2021-27137 (DD-WRT). CISA remediation deadline was July 24, 2026; still in catalog.

CWE-121 · CNA: mitre · CVSS v3.1 · 6 references · NVD status: Analyzed · KEV due July 24, 2026

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).

Lifecycle

Complete event history — 5 events, chronological
Date	Event	Detail
February 10, 2021	Reserved	Reserved by mitre
July 21, 2026	KEV ADDED	Added to CISA KEV, remediation due 2026-07-24
July 21, 2026	Published	Published (CNA: mitre)
July 22, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2021-27137 (DD-WRT). Public exploit reference added.
July 25, 2026	DUE DATE PASSED	DUE DATE PASSED — CVE-2021-27137 (DD-WRT). CISA remediation deadline was July 24, 2026; still in catalog.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
DD-WRT	DD-WRT	—	—	—

Weaknesses

CWE-121

References (6)

https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html [Exploit, Third Party Advisory]
https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/ [Exploit, Third Party Advisory]
https://svn.dd-wrt.com/changeset/45724 [Patch]
https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/ [Exploit, Third Party Advisory]
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137 [US Government Resource]
https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo [Exploit]

Authoritative record: CVE-2021-27137 at cve.org

Vendors: dd-wrt

Weaknesses: CWE-121

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-27137 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.