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Vulnerability record · CVE-2021-34991 · published 15 November 2021

CVE-2021-34991: Netgear ex3700 firmware stack-based buffer overflow vulnerability

Netgear · Ex3700 Firmware

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of NETGEAR R6400v2 1.0.4.106_10.0.80 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the UPnP service, which listens on TCP port 5000 by default. When parsing the uuid request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14110.

8.8 CVSS 3.1 High EPSS 5.7% · top 7.3% CWE-121 · Stack-based buffer overflowCWE-787 · Out-of-bounds write
8.8CVSS 3.1 base score, v2 8.3
5.7%EPSS exploitation probability, 30 days
NoNot in CISA KEV
44Affected 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 R6400v2 1.0.4.106_10.0.80 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the UPnP service, which listens on TCP port 5000 by default. When parsing the uuid request header, the process does not properly validate the length of user-supplied data prior to copying it to a fixed-length stack-based buffer. An attacker can leverage this vulnerability to execute code in the context of root. Was ZDI-CAN-14110.

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

Affected products

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

References

LinkTags
https://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021- Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-1303/ Third Party AdvisoryVDB Entry
https://kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overflow-on-Multiple-Products-PSV-2021- Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-21-1303/ 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-2021-34991), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.