What is CVE-2021-35034?

CVE-2021-35034 is a high-severity vulnerability in Zyxel Nbg6604, classified under Insufficient Session Expiration. CVSS score: 7.4/10. Published 2021-12-29.

How severe is CVE-2021-35034?

High severity. CVSS v3 base score is 7.4 out of 10.

Vulnerability in Zyxel Nbg6604

CVE-2021-35034

An insufficient session expiration vulnerability in the CGI program of the Zyxel NBG6604 firmware could allow a remote attacker to access the device if the correct token can be intercepted.

Published 2021-12-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.010 (62.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 63rd percentile — 62.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Zyxel Nbg6604
Zyxel Nbg6604 Firmware
Zyxel Nbg6604 Series Firmware — versions 1.00(ABIR.8)C0

Weakness classification (CWE)

CWE-613 — Insufficient Session Expiration

References

www.zyxel.com/support/Zyxel_security_advisory_for_sensitive_information_vulnera… (Vendor Advisory)

Frequently asked questions

What is CVE-2021-35034?: CVE-2021-35034 is a high-severity vulnerability in Zyxel Nbg6604, classified under Insufficient Session Expiration. CVSS score: 7.4/10. Published 2021-12-29.
How severe is CVE-2021-35034?: High severity. CVSS v3 base score is 7.4 out of 10.