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A720R Firmware CVE-2021-35327

CRITICAL
Missing Authorization (CWE-862)
2021-08-05 cve@mitre.org
Authentication Bypass A720R Firmware TOTOLINK
9.8
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
CWE-862
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Authorization checks on every request
MITRE ATT&CK

1 technique across 1 tactic: Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Impact

CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived

A remote attacker could access resources or perform actions without proper authorization checks by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.
Act Now Prioritize within 24-48h. Why: CRITICAL severity + public POC available.
No patch listed yet 1.4% exploitation probability (EPSS)

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AnalysisAI

A vulnerability in TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to start the Telnet service, then login with the default credentials via a crafted POST request. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Implement role-based access control, validate authorization on every request server-side, apply principle of least privilege.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified as Missing Authorization (CWE-862), which allows attackers to access resources or perform actions without proper authorization checks. A vulnerability in TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to start the Telnet service, then login with the default credentials via a crafted POST request. Affected products include: Totolink A720R Firmware.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

NVD PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

DescriptionNVD

A vulnerability in TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to start the Telnet service, then login with the default credentials via a crafted POST request.

Threat Intelligence Overview

EPSS Score
1.4%
Top 31% exploitable
Exploit
POC
Public exploit code exists
Data Quality
3 sources
Confidence: Low
NVD CVE.org EPSS GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC Yes
EPSS 1.4%
Patch available No
Active threat No
Deciding rule
CRITICAL severity + public POC available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

70
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +49
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:o:totolink:a720r_firmware:4.1.5cu.470_b20200911:*:*:*:*:*:*:*

More in A720R Firmware

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CVE-2021-35324 CRITICAL POC
9.8 Aug 05

A vulnerability in the Form_Login function of TOTOLINK A720R A720R_Firmware V4.1.5cu.470_B20200911 allows attackers to b
CVE-2021-27710 CRITICAL POC
9.8 Apr 14

Command Injection in TOTOLINK X5000R router with firmware v9.1.0u.6118_B20201102, and TOTOLINK A720R router with firmwar
CVE-2021-27708 CRITICAL POC
9.8 Apr 14

Command Injection in TOTOLINK X5000R router with firmware v9.1.0u.6118_B20201102, and TOTOLINK A720R router with firmwar
CVE-2025-60683 MEDIUM POC
6.5 Nov 13

A command injection vulnerability exists in the ToToLink A720R Router firmware V4.1.5cu.614_B20230630 within the sysconf
CVE-2022-36610 HIGH POC
7.8 Aug 29

TOTOLINK A720R V4.1.5cu.532_B20210610 was discovered to contain a hardcoded password for root at /etc/shadow.sample. Rat
CVE-2022-36456 HIGH POC
7.8 Aug 25

TOTOLink A720R V4.1.5cu.532_B20210610 was discovered to contain a command injection vulnerability via the username param
CVE-2021-35326 HIGH POC
7.5 Aug 05

A vulnerability in TOTOLINK A720R router with firmware v4.1.5cu.470_B20200911 allows attackers to download the configura
CVE-2021-35325 HIGH POC
7.5 Aug 05

A stack overflow in the checkLoginUser function of TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers
CVE-2022-38535 HIGH POC
7.2 Sep 15

TOTOLINK-720R v4.1.5cu.374 was discovered to contain a remote code execution (RCE) vulnerability via the setTracerouteCf
CVE-2022-38534 HIGH POC
7.2 Sep 15

TOTOLINK-720R v4.1.5cu.374 was discovered to contain a remote code execution (RCE) vulnerability via the setdiagnosicfg

CVE-2025-4270 MEDIUM POC
6.9 May 05

A vulnerability was found in TOTOLINK A720R 4.1.5cu.374. Rated medium severity (CVSS 6.9), this vulnerability is remotel
CVE-2025-4269 MEDIUM POC
6.9 May 05

A vulnerability was found in TOTOLINK A720R 4.1.5cu.374 and classified as critical.cgi of the component Log Handler. Rat

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