What is CVE-2021-34991?

CVE-2021-34991 is a high-severity vulnerability in NETGEAR Cax80, classified under Stack-based Buffer Overflow. CVSS score: 8.8/10. Published 2021-11-15.

How severe is CVE-2021-34991?

High severity. CVSS v3 base score is 8.8 out of 10.

Buffer overflow in NETGEAR Cax80

CVE-2021-34991

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.

Vulnerability class: Buffer Overflow

Published 2021-11-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.057 (92.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 92.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.057 · newest: 0.057 · change: 0.000

Affected products

Weakness classification (CWE)

References

www.zerodayinitiative.com/advisories/ZDI-21-1303/ (VDB Entry, Third Party Advisory)
kb.netgear.com/000064361/Security-Advisory-for-Pre-Authentication-Buffer-Overfl… (Vendor Advisory)

Frequently asked questions

What is CVE-2021-34991?: CVE-2021-34991 is a high-severity vulnerability in NETGEAR Cax80, classified under Stack-based Buffer Overflow. CVSS score: 8.8/10. Published 2021-11-15.
How severe is CVE-2021-34991?: High severity. CVSS v3 base score is 8.8 out of 10.