CVE-2021-27137

HighCVSS 8.1/10Known exploited (CISA KEV)Last modified Jul 22, 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).

Metrics

CVSS 3.1 8.1/10CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness enumeration

CWE-121

Affected software

No affected versions have been published.

Timeline

Published
Jul 16, 2026
Last modified
Jul 22, 2026
Added to CISA KEV
Jul 21, 2026
NVD status
Analyzed

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CVE-2021-27137: High severity, CVSS 8.1 | Vulnix