CVE-2021-27137
DD-WRT DD-WRT
Summary
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. Exploit…
Published: 2026-07-16 · In KEV since: 2026-07-21
Analysis
🔴 Critical — actively exploited
Weakness: Buffer Overflow (CWE-121). Writes past the buffer; memory corruption or RCE.
How it's exploited: Exploitable over the network (internet-reachable), unauthenticated, no user interaction, with high complexity.
Impact: Full compromise (confidentiality, integrity and availability).
Status: Active exploitation confirmed by CISA (KEV).
- Patch now: it is in CISA's actively-exploited catalog (KEV), with a deadline.
- Reduce exposure: keep it off the internet; firewall, VPN or network segmentation.
- Detect: turn this CVE into detection rules.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
The vector encodes how it's exploited (translated above, in the analysis). Break it down in the CVSS tool →
Sources: CISA KEV · EPSS · FIRST.org · NVD. Analysis derived from the CVSS vector and exploitation status (no AI). Informational; always verify against the vendor's official advisory.