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Vulnerability record · CVE-2021-27239 · published 29 March 2021

CVE-2021-27239: Netgear d6220 firmware stack-based buffer overflow vulnerability

Netgear · D6220 Firmware

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400 and R6700 firmware version 1.0.4.98 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the upnpd service, which listens on UDP port 1900 by default. A crafted MX header field in an SSDP message can trigger an overflow of a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-11851.

8.8 CVSS 3.1 High EPSS 0.74% · top 46.3% CWE-121 · Stack-based buffer overflow
8.8CVSS 3.1 base score, v2 8.3
0.74%EPSS exploitation probability, 30 days
NoNot in CISA KEV
35Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400 and R6700 firmware version 1.0.4.98 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the upnpd service, which listens on UDP port 1900 by default. A crafted MX header field in an SSDP message can trigger an overflow of a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-11851.

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

35 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-o Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-206/ Third Party AdvisoryVDB Entry
https://kb.netgear.com/000062820/Security-Advisory-for-Stack-based-Buffer-Overflow-Remote-Code-Execution-Vulnerability-o Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-206/ Third Party AdvisoryVDB Entry

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-27239), CISA KEV, FIRST EPSS (scores of 2026-10-16). This page is refreshed as NVD updates the record.