CVE-2026-75616 Overview
CVE-2026-75616 is an OS command injection vulnerability [CWE-78] in the web management interface of the TP-Link Archer C20 v6 router firmware. The flaw resides in code paths that process certain WAN-related configuration operations. Insufficient input validation allows an authenticated administrator on the adjacent network to inject arbitrary operating system commands. Successful exploitation yields command execution with elevated privileges on the device. An attacker can compromise the confidentiality, integrity, and availability of the router and all network traffic traversing it.
Critical Impact
Authenticated attackers on the adjacent network can execute arbitrary system commands on the router, resulting in full device compromise and interception of network traffic.
Affected Products
- TP-Link Archer C20 v6 firmware (prior to version 6.46)
- Web management interface WAN configuration handlers
- Consumer wireless router deployments running vulnerable firmware
Discovery Timeline
- 2026-08-19 - CVE-2026-75616 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2026-75616
Vulnerability Analysis
The vulnerability is a classic OS command injection [CWE-78] in the router's HTTP-based management interface. When an authenticated administrator submits certain WAN configuration parameters, the firmware passes user-supplied values into a shell context without adequate sanitization or safe-argument handling. Metacharacters such as ;, |, &, backticks, and $() are interpreted by the underlying shell instead of being treated as literal data. The resulting commands run under the privileges of the web management daemon, which on consumer routers typically executes as root. The EPSS score is 1.135% at the 63.99 percentile, reflecting moderate near-term exploitation probability.
Root Cause
The root cause is improper neutralization of special elements used in an OS command. The WAN configuration handler concatenates administrator-supplied strings into a shell invocation rather than using parameterized execution such as execve with an argument vector. No allow-list validation or shell-metacharacter escaping is applied before the values reach the command interpreter.
Attack Vector
Exploitation requires network adjacency to the device, such as the local LAN or Wi-Fi, and valid administrator credentials. The attacker authenticates to the web management interface, then submits a crafted WAN configuration request containing shell metacharacters appended to an otherwise valid parameter. The injected payload executes with root privileges, enabling persistence, DNS hijacking, traffic interception, credential harvesting, and pivoting into the internal network.
Because no verified proof-of-concept has been published, technical readers should consult the TP-Link Archer C20 Firmware page and TP-Link FAQ #5252 for vendor-provided guidance.
Detection Methods for CVE-2026-75616
Indicators of Compromise
- Unexpected outbound connections initiated by the router to unknown IP addresses or dynamic DNS providers.
- Modified DNS server settings on the router that do not match the ISP-assigned or administrator-configured values.
- Configuration backups containing shell metacharacters (;, |, `, $()) in WAN parameter fields.
- New or altered administrative accounts and unexpected firmware or configuration changes.
Detection Strategies
- Inspect router web-interface access logs for POST requests to WAN configuration endpoints containing shell metacharacters in parameter values.
- Monitor for anomalous administrative logins from unusual client MAC addresses or off-hours sessions.
- Baseline expected DNS, NTP, and upstream gateway values, and alert on deviations pulled from device configuration.
Monitoring Recommendations
- Forward router syslog and management-interface events to a centralized log platform for correlation.
- Monitor LAN egress for traffic patterns consistent with router-originated command-and-control activity.
- Track firmware version reporting across the fleet to identify devices still running vulnerable builds.
How to Mitigate CVE-2026-75616
Immediate Actions Required
- Upgrade Archer C20 v6 devices to firmware version 6.46 or later using the TP-Link Archer C20 Firmware 6.46 download.
- Rotate administrator credentials and disable any default or reused passwords on the web management interface.
- Restrict management interface access to trusted wired hosts and disable remote (WAN-side) management.
- Audit current WAN configuration for injected values and reset the device to factory defaults if tampering is suspected.
Patch Information
TP-Link has published updated firmware for the Archer C20 v6 that addresses the input validation flaw in the WAN configuration handlers. Refer to the TP-Link Archer C20 v6 Firmware page for the latest build and to TP-Link FAQ #5252 for upgrade instructions.
Workarounds
- Disable the web management interface on the WAN side and limit LAN-side access to a dedicated management VLAN.
- Enforce strong, unique administrator passwords and change the default admin username where supported.
- Segment untrusted Wi-Fi clients away from the router's management subnet to remove adjacent-network attack paths.
- Replace end-of-life consumer routers with actively supported models where firmware updates are no longer produced.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
