Is CVE-2021-20124 (Draytek VigorConnect Path Traversal Vulnerability) being exploited in the wild?

What this exploitation status means for defenders

For defenders, “being exploited in the wild” changes the question from theoretical exposure to active incident likelihood. CISA’s KEV listing is the practical signal that the issue has crossed that threshold, so the right response is inventory, prioritisation and containment, not routine backlog treatment. Confirm whether the product exists anywhere in your environment, including forgotten lab, remote-access or partner-facing instances.

When a flaw is already being used by attackers, exposure is often wider than the known internet-facing service. Review asset registers, configuration management data and network telemetry for the vendor name, product family and the specific WebServlet file download path so you can find both direct exposure and any indirect exposure through load balancers, reverse proxies or management networks.

Internal reference points that help here include Zero-Day and Exploited Vulnerabilities Guide for triage discipline and Vulnerability Management Guide for prioritisation, exception handling and verification. Treat the presence of active exploitation as a reason to accelerate the same workflow, not to invent a separate process.

Why path traversal in a download endpoint is operationally serious

A path traversal flaw in a file download function is dangerous because it can let an attacker request files outside the intended directory boundary. In a product like VigorConnect, that may expose configuration data, cached credentials, session material or other internal files if the server-side access control is weak enough.

The security issue is not just that a file is read incorrectly, it is that the application is making a trust decision about user-supplied path input. If that input is insufficiently normalised or filtered, the endpoint can become a straightforward way to pivot from ordinary web access into broader system disclosure. That makes the flaw especially attractive for opportunistic scanning and automated exploitation.

For a broader attack-path perspective, Web Application Attacks Guide helps place path traversal alongside other server-side input handling failures. On the public side, the authoritative references are the CVE Program record and the NIST National Vulnerability Database entry, which should be used for canonical record lookups and product details.

What to do when patching must wait

If remediation cannot happen immediately, reduce exposure by taking the vulnerable service out of direct reach wherever possible. The most effective interim steps are to restrict who can reach the WebServlet endpoint, limit the download function to trusted administrative paths, and place the product behind tightly scoped network controls rather than general user access.

Also look for signs of earlier compromise, because active exploitation means the question is not only “can it be attacked?” but “has it already been used against us?”. Review web logs, reverse-proxy logs and host telemetry for unusual traversal strings, repeated download attempts, unexpected file names, error bursts and access to sensitive directories. If the product handles credentials or configuration material, rotate anything the exposure may have revealed.

Use the CISA Known Exploited Vulnerabilities Catalog as the prioritisation anchor and the vendor advisory for exact remediation instructions. If this is a remotely reachable asset, FIRST EPSS can add useful context for urgency, but it should complement, not replace, the KEV-driven response.

Risk and Threat Considerations

Path traversal in an exposed download endpoint creates both disclosure risk and a practical foothold for follow-on abuse. Once an attacker can read arbitrary files, they may recover configuration data, secrets, logs or session material that helps them move from one vulnerable product to broader environment access.

Failure mechanism: The application trusts user-controlled path input and fails to confine file access to the intended directory, allowing traversal outside the allowed download scope.

Impact: An attacker can extract sensitive local files, identify useful credentials or configuration details, and use that information for lateral movement or persistence if the system is not isolated.

Practitioner Guidance

What to verify: Confirm whether any VigorConnect instance is reachable from untrusted networks, whether the vulnerable download path is exposed through alternate hostnames, and whether compensating controls actually block traversal attempts rather than only the visible URL path.

Decision rule: If the system is internet-facing or holds administrative configuration data, treat this as urgent containment plus patching. If patching must wait, disable or restrict the affected function rather than relying on detection alone.

Practitioner takeaway: KEV-listed exploitation shifts the problem from vulnerability management to incident-style response, so speed, exposure reduction and compromise assessment matter more than debating whether the flaw is “serious enough.”

Related resources from NHI Mgmt Group

• Guide: IoT Security Guide
• How do you patch or mitigate CVE-2021-20124 (Draytek VigorConnect Path Traversal Vulnerability)?
• CVE-2021-20124 (Draytek VigorConnect Path Traversal Vulnerability)
• How do you patch or mitigate CVE-2021-20123 (Draytek VigorConnect Path Traversal Vulnerability)?
• CVE-2021-20123 (Draytek VigorConnect Path Traversal Vulnerability)