Actively exploited
Listed in CISA’s Known Exploited Vulnerabilities catalog since July 21, 2026.
CVE-2021-27137
DD-WRT Stack-Based Buffer Overflow Vulnerability
Added to KEV July 21, 2026
Alert details
- Source feed
- CISA KEV
- CVE ID
- CVE-2021-27137
- CWE
- CWE-121
- Affected products
- DD-WRT · DD-WRT DD-WRT
What happened
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.
What it means for your business
DD-WRT DD-WRT is listed in CISA's Known Exploited Vulnerabilities catalog (CVE-2021-27137). 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. CISA remediation due date: 2026-07-24. PremierePC tracks KEV alerts for Upstate SC businesses — patch or open a ticket if you need help verifying exposure.
Required action
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.
CISA due date: July 24, 2026
Sources
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