CVE-2021-35033

Exp

A vulnerability in specific versions of Zyxel NBG6818, NBG7815, WSQ20, WSQ50, WSQ60, and WSR30 firmware with pre-configured password management could allow an attacker to obtain root access of the device, if the local attacker dismantles the device and uses a USB-to-UART cable to connect the device, or if the remote assistance feature had been enabled by an authenticated user.

Published: 2021-11-23 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-35033 is rated Exploit Available (57.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.40%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-35033

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-35033

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.11% 0.40% +0.28%
2 2026-03-17 0.04% 0.11% +0.08%
3 2025-04-10 — 0.04% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-35033

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
6.9 2.0 MEDIUM
AV:L/AC:M/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 3.4 10.0 [email protected]

Weakness enumeration for CVE-2021-35033

Affected software / configurations for CVE-2021-35033

Vendor Product Version Raw CPE
zyxel nbg6818_firmware < 1.00\(absc.5\)c0 cpe:2.3:o:zyxel:nbg6818_firmware:*:*:*:*:*:*:*:*
zyxel nbg7815_firmware < 1.00\(absk.7\)c0 cpe:2.3:o:zyxel:nbg7815_firmware:*:*:*:*:*:*:*:*
zyxel wsq20_firmware < 1.00\(abof.11\)c0 cpe:2.3:o:zyxel:wsq20_firmware:*:*:*:*:*:*:*:*
zyxel wsq50_firmware < 2.20\(abkj.7\)c0 cpe:2.3:o:zyxel:wsq50_firmware:*:*:*:*:*:*:*:*
zyxel wsq60_firmware < 2.20\(abnd.8\)c0 cpe:2.3:o:zyxel:wsq60_firmware:*:*:*:*:*:*:*:*
zyxel wsr30_firmware < 1.00\(abmy.12\)c0 cpe:2.3:o:zyxel:wsr30_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-35033

cvelogic Threat Intelligence