high Known exploitedREV. 01
CVE-2021-27137DD-WRT — UPnP stack buffer overflow RCE
The DD-WRT router firmware (DD-WRT builds before 45724) copies data unsafely in its Universal Plug and Play (UPnP) service. An unauthenticated attacker in reach sends a crafted discovery (M-SEARCH) request to overflow a buffer and run code on the router. UPnP is off by default.
Read the risk
THE VITAL STATS- CVSS score
- 8.1/ 10 CVSS v3.1
- EPSS probability
- 4% Likelihood of exploitation
- Attack complexity
- High Conditions needed to exploit
- Known exploited
- Yes — CISA KEV
- CVE published
- 2026-07-16
- Added to KEV
- 2026-07-21
- Exploit published
- Yes
- Confidence
- high
- Kill chain
- initial access
- MITRE ATT&CK
- T1190
- Severity
- high
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Attacker needsNetwork reach to the router's UPnP (SSDP) listener; UPnP must be enabled by the user (off by default and internal-interface only by default).
Fixed inDD-WRT 45724
Behind the card
5 REFERENCES- 01CVE recordNVD recordnvd.nist.gov
- 02CISACISA Known Exploited Vulnerabilities catalogcisa.gov
- 03Vendor advisorysvn.dd-wrt.comsvn.dd-wrt.com
- 04Exploitsecurityaffairs.comsecurityaffairs.com
- 05Exploitssd-disclosure.comssd-disclosure.com
Field-level provenanceTRACE THE SOURCES +
Which source supports each field, when it was retrieved, and who extracted it.
| Fields | Source | Retrieved | Extractor | Confidence |
|---|---|---|---|---|
| cvss, exploitation.attack_complexity, exploitation.exploit_available, references, published_at | nvd.nist.gov | 2026-09-22 | scrty-crds-pipeline/0.1 | high |
| exploitation.known_exploited, exploitation.kev_added | cisa.gov | 2026-09-22 | scrty-crds-pipeline/0.1 | high |
| epss | api.first.org | 2026-09-22 | scrty-crds-pipeline/0.1 | high |
| title, summary, severity, remediation, mitre_attack, kill_chain, recommended_action, confidence, tags, exploitation.prerequisites | nvd.nist.gov | 2026-09-22 | claude-code | high |
Printing history
THE RECORD- r1Initial base card
First printing. This card has not been reprinted since publication.