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Vulnerabilities / CVE-2021-27137

CVE-2021-27137

Published 2026-07-16 · published (not yet in NVD)

CVE-2021-27137

Exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2026-07-21, with a fix-by date of 2026-07-24. Patch it first.

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.

8.1 HIGH
CVSS 3.1 · CNA
4.0%
chance of exploitation in the next 30 days (EPSS; higher than 90% of CVEs)

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. Exploitation requires the DD-WRT user to enable UPnP (which is off by default, and only listens on internal interfaces by default). This occurs in ssdp_msearch (reachable by an M-SEARCH request).

Scores

Affected products

  • DD-WRT DD-WRT: < 45724

Weakness: CWE-121

5 references (advisories, patches, write-ups)

Sources: CVE.org, FIRST EPSS. Missing ones did not answer or have no record yet.

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