{"id":"CVE-2021-27137","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-27137","generatedAt":"2026-10-31T05:05:45.419Z","title":"DD-WRT Stack-Based Buffer Overflow Vulnerability","description":"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).","published":"2026-07-16T18:16:39.000Z","lastModified":"2026-07-22T05:17:07.000Z","status":"Analyzed","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},"cwe":["CWE-121"],"affected":["dd-wrt/dd-wrt"],"epss":{"score":0.03995,"percentile":0.90507,"date":"2026-10-30","history":[]},"kev":{"listed":true,"dateAdded":"2026-07-21","dueDate":"2026-07-24","knownRansomwareCampaignUse":"Unknown","notes":"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.\nThis vulnerability affects a common open-source component, third-party library, proprietary implementation, or a protocol used by different products. Please check with specific vendors for information on patching status. For more information, please see: https://svn.dd-wrt.com/changeset/45724 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2021-27137"},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"urgent","text":"Known to be exploited in the wild (CISA KEV, CISA remediation deadline 24 July 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise."},"changes":[],"references":[{"url":"https://securityaffairs.com/193290/uncategorized/iot-botnet-c0xmo-adds-competitor-killing-capability.html","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://svn.dd-wrt.com/changeset/45724","tags":["Patch"],"source":"cve@mitre.org"},{"url":"https://www.bleepingcomputer.com/news/security/c0xmo-botnet-spreads-via-dd-wrt-router-flaw-kills-rival-malware/","tags":["Exploit","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://www.fortinet.com/blog/threat-research/inside-cross-platform-propagation-of-new-gafgyt-variant-c0xmo","tags":["Exploit"],"source":"cve@mitre.org"},{"url":"https://ssd-disclosure.com/ssd-advisory-dd-wrt-upnp-buffer-overflow/","tags":["Exploit","Third Party Advisory"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-27137","tags":["US Government Resource"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-27137","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}