CVE-2021-27137
Prioritize patching. It under exploitation confirmed by CISA.
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.
A flaw in DD-WRT's UPnP service allows an attacker on the local network to crash the router or potentially run malicious code by sending a specially crafted network request, but only if UPnP is enabled.
An unsafe strcpy in ssdp.c's ssdp_msearch function, reachable via M-SEARCH UPnP discovery requests, enables stack buffer overflow on an internal fixed buffer. Attack vector is network (local/LAN), requires UPnP enabled (disabled by default), and can lead to denial of service or code execution.