Skip to main content

A720R Firmware CVE-2021-35325

HIGH
Out-of-bounds Write (CWE-787)
2021-08-05 cve@mitre.org
7.5
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, write limits
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

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

Impact

CVSS score of 7.5 (HIGH). 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 write data beyond allocated buffer boundaries leading to code execution or crashes by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity + EPSS > 10%.
No patch listed yet 13.3% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAI

A stack overflow in the checkLoginUser function of TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to cause a denial of service (DOS). Rated high severity (CVSS 7.5), 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. Validate write boundaries, use memory-safe languages, enable compiler protections (ASLR, stack canaries).

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Out-of-bounds Write (CWE-787), which allows attackers to write data beyond allocated buffer boundaries leading to code execution or crashes. A stack overflow in the checkLoginUser function of TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to cause a denial of service (DOS). Affected products include: Totolink A720R Firmware.

Know when A720R Firmware gets its next vulnerability

  • Watch products and get an email when something new is published
  • Check this CVE against your own stack and servers
  • Exploit and PoC references, threat intelligence from 22 sources

No credit card · 7-day full trial

Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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
None
Integrity
None
Availability
High

DescriptionNVD

A stack overflow in the checkLoginUser function of TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to cause a denial of service (DOS).

Threat Intelligence Overview

EPSS Score
13.3%
Top 4% exploitable
Exploit
POC
Public exploit code exists
Data Quality
3 sources
Confidence: Low

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 HIGH
CISA KEV No
Public POC Yes
EPSS 13.3%
Patch available No
Active threat Yes
Deciding rule
HIGH severity + EPSS > 10%
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

71
Low Medium High Critical
KEV: 0
EPSS: +13
CVSS: +38
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:o:totolink:a720r_firmware:4.1.5cu.470_b20200911:*:*:*:*:*:*:*
CVE-2021-35327 CRITICAL POC
9.8 Aug 05

A vulnerability in TOTOLINK A720R A720R_Firmware v4.1.5cu.470_B20200911 allows attackers to start the Telnet service, th

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-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

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy