CVE-2021-27137 KEV
8.1
HIGH · CVSS 3.1 · EPSS 4% (pctl 90)
Patch first
On CISA KEV — known exploited in the wild, due 2026-07-24.
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).
Scoring
| CVSS | 8.1 (HIGH, v3.1) |
|---|---|
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H |
| EPSS | 4% — more likely to be exploited than 90% of all CVEs |
| Weakness | CWE-121 |
| On CISA KEV | yes — remediate by 2026-07-24 |
| Public exploit | none known |
| Published | 2026-07-16 |
| Last modified | 2026-07-22 |
CISA KEV
| Name | DD-WRT Stack-Based Buffer Overflow Vulnerability |
|---|---|
| Added | 2026-07-21 |
| Due | 2026-07-24 |
| Vendor / product | DD-WRT / DD-WRT |
| Ransomware use | none reported |
Affected (1)
| Vendor | Product |
|---|---|
| dd-wrt | dd-wrt |
References
- https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html
- https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
- https://svn.dd-wrt.com/changeset/45724
- https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/
- https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo
- https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137
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