An insufficient session expiration vulnerability in the CGI program of the Zyxel NBG6604 firmware could allow a remote attacker to access t…

published 2021-12-29 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21681

cvss: 7.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.1%; EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

zyxel nbg6604_firmware 1.00\(abir.9\)c0

Exploit prediction

1.08% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.4	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD	3.1	9.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD	2.0	6.4	AV:N/AC:L/Au:N/C:P/I:P/A:N

Affected products

Zyxel NBG6604 series firmware

Classification

Weakness

CWE-613 DEPRECATED: Insufficient Session Expiration

References

zyxel.com /support/Zyxel_security_advisory_for_sensitive_information_vulnerabilities_of_NBG6604_home_router.shtml
vendor-advisory

Sources

CVE List CVE-2021-35034
NVD CVE-2021-35034

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary