CVE-2024-41334 Overview
CVE-2024-41334 is a certificate validation flaw [CWE-295] affecting a broad range of DrayTek Vigor routers. The affected firmware does not verify TLS certificates when retrieving APPE (Application Enforcement) modules from update servers. Attackers positioned on the network path can substitute a malicious server, deliver crafted APPE modules, and achieve arbitrary code execution on the device. The issue impacts Vigor 165/166, 2620/LTE200, 2860/2925, 2862/2926, 2133/2762/2832, 2135/2765/2766, 2865/2866/2927, 2962/3910, and 3912 across multiple firmware branches.
Critical Impact
An attacker who can intercept or redirect the router's module-fetch traffic gains code execution on the router itself, providing persistent control over network edge infrastructure.
Affected Products
- DrayTek Vigor 165/166 firmware prior to v4.2.6, Vigor 2620/LTE200 prior to v3.9.8.8, Vigor 2860/2925 prior to v3.9.7
- DrayTek Vigor 2862/2926 prior to v3.9.9.4, Vigor 2133/2762/2832 prior to v3.9.8, Vigor 2135/2765/2766 prior to v4.4.5.1
- DrayTek Vigor 2865/2866/2927 prior to v4.4.5.3, Vigor 2962/3910 prior to v4.3.2.7, Vigor 3912 prior to v4.3.5.2, and Vigor 2925 up to v3.9.6
Discovery Timeline
- 2025-02-27 - CVE-2024-41334 published to the National Vulnerability Database (NVD)
- 2026-07-05 - Last updated in NVD database
Technical Details for CVE-2024-41334
Vulnerability Analysis
DrayTek Vigor routers periodically fetch APPE modules used for application enforcement and traffic classification. The firmware performs these fetches over TLS but does not validate the server certificate. Any endpoint responding on the expected host and port is accepted as authentic, regardless of certificate issuer or subject.
An attacker in a suitable network position can present a self-signed or attacker-controlled certificate. The router then downloads and loads the attacker's binary module. Because APPE modules are executed with router privileges, successful delivery yields arbitrary code execution on the device.
Root Cause
The root cause is improper certificate validation [CWE-295] in the module update client. The TLS client accepts the server's certificate chain without verifying the trust anchor, hostname, or revocation state. This defeats the authentication guarantee that TLS is intended to provide for the module distribution channel.
Attack Vector
Exploitation requires the attacker to intercept or redirect the router's outbound update traffic. Practical paths include DNS poisoning on the LAN or upstream, BGP or route hijacks against the update infrastructure, rogue upstream ISP equipment, or compromise of a device between the router and the legitimate server. The CVSS vector indicates network-adjacent exploitation with low complexity, low privileges, and no user interaction. Successful exploitation compromises confidentiality, integrity, and availability of the router.
No verified public exploit code is available. Technical detail is described in the Faraday advisory on DrayTek router vulnerabilities.
Detection Methods for CVE-2024-41334
Indicators of Compromise
- Outbound TLS connections from a Vigor router to hosts that do not resolve to DrayTek-owned infrastructure, particularly on module update ports.
- Unexpected APPE module files, timestamps, or version strings observable through the router's management interface or SNMP counters.
- Router-originated traffic patterns inconsistent with the device's normal baseline, such as new outbound connections, DNS lookups to unfamiliar domains, or tunneling behavior.
Detection Strategies
- Inspect DNS resolutions requested by the router and alert on lookups for DrayTek update hostnames that resolve to non-DrayTek IP ranges.
- Capture TLS handshakes originating from the router and flag certificates that are not issued by DrayTek's expected certificate authority.
- Compare firmware and APPE module hashes and versions across a fleet of routers to identify outliers.
Monitoring Recommendations
- Forward router syslog, DNS, and NetFlow telemetry into a centralized analytics platform for correlation and long-term retention.
- Alert on configuration changes, administrative logins, and firmware or module updates that occur outside change windows.
- Baseline the router's normal update cadence and destinations, then alert on deviations.
How to Mitigate CVE-2024-41334
Immediate Actions Required
- Upgrade each affected model to the fixed firmware version listed in the Affected Products section.
- Restrict management and update traffic to trusted network paths, and disable WAN-side management where not required.
- Rotate router administrator credentials and pre-shared keys after patching, in case the device was previously exposed.
Patch Information
DrayTek has released fixed firmware for every affected model. Apply at minimum: Vigor 165/166 v4.2.6, Vigor 2620/LTE200 v3.9.8.8, Vigor 2860/2925 v3.9.7, Vigor 2862/2926 v3.9.9.4, Vigor 2133/2762/2832 v3.9.8, Vigor 2135/2765/2766 v4.4.5.1, Vigor 2865/2866/2927 v4.4.5.3, Vigor 2962/3910 v4.3.2.7, and Vigor 3912 v4.3.5.2. Vigor 2925 units at v3.9.6 or earlier must move to a supported branch, since the End-of-Life status of that model should be confirmed with DrayTek support.
Workarounds
- Block or proxy the router's outbound update traffic through a trusted egress point that enforces certificate pinning until firmware can be applied.
- Segment routers onto a management VLAN and restrict which upstream resolvers and gateways they can use, reducing opportunities for interception.
- Monitor for anomalous outbound TLS sessions from the router and treat any unverifiable certificate as an incident until patched.
# Example: restrict router egress to trusted resolvers and drop other DNS
# (apply on the upstream firewall, not the vulnerable Vigor itself)
iptables -A FORWARD -s <router_ip> -p udp --dport 53 -d <trusted_resolver> -j ACCEPT
iptables -A FORWARD -s <router_ip> -p udp --dport 53 -j DROP
iptables -A FORWARD -s <router_ip> -p tcp --dport 53 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
