CVE-2021-27137
Stack-Based Buffer Overflow in DD-WRT. CISA confirmed attackers exploit it and added it to its Known Exploited Vulnerabilities catalog on 21 July 2026.
- Product
- DD-WRT
- Added to CISA's catalog
- Federal fix-by date
- Ransomware
- No known use in ransomware campaigns
- Vendor advisories
- Sources
- CISA’s catalog, NVD entry
CISA’s description.
DD-WRT contains a stack-based buffer overflow vulnerability that could allow an unauthenticated attacker to overflow an internal buffer used by UPnP and trigger a code execution vulnerability.
Every flaw CISA confirmed exploited in the last 30 days is on the exploit watch. This is not security advice. Check the vendor’s advisory before acting. From CISA’s catalog of 4 November 2026.