CVE-2026-75616 in Archer C20
Summary
by MITRE • 08/20/2026
An OS command injection vulnerability exists in the web management interface of Archer C20 v6 firmware when processing certain WAN-related configuration operations. An authenticated administrator may exploit insufficient input validation to execute arbitrary system commands, potentially resulting in full device compromise.
Successful exploitation may allow arbitrary command execution with elevated privileges, compromising the confidentiality, integrity, and availability of the affected device and network traffic passing through it.
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Analysis
by VulDB Data Team • 08/20/2026
The vulnerability identified in Archer C20 v6 firmware represents a critical OS command injection flaw within its web management interface. This specific weakness manifests during the processing of WAN-related configuration operations, where the application fails to adequately sanitize user-supplied input before constructing system-level commands for execution. The root cause lies in insufficient validation and encoding mechanisms that allow an attacker to inject malicious shell metacharacters or logic operators into form fields intended for standard network parameters such as IP addresses, DNS servers, or gateway settings. Because this interface is designed for administrative configuration, it typically operates with high privileges, meaning any command executed through this vector inherits the permissions of the underlying service account, which often includes root-level access on embedded Linux devices like routers and wireless access points.
Exploitation requires an authenticated administrator to interact with the vulnerable endpoint. While authentication provides a layer of defense against unauthenticated remote attackers, it does not mitigate risks posed by insider threats or compromised administrative credentials. An attacker who has obtained valid login details can manipulate specific WAN configuration parameters to trigger arbitrary command execution on the device's operating system. The technical mechanism involves injecting commands that bypass intended logic, allowing for the creation of new user accounts, modification of firewall rules, installation of persistent backdoors, or exfiltration of sensitive network data. This capability effectively grants full control over the physical hardware and its immediate network environment.
The operational impact of this vulnerability is severe, extending beyond the compromise of a single device to potentially affecting the entire local area network connected through it. By achieving arbitrary command execution with elevated privileges, an attacker can intercept, modify, or drop traffic passing through the router, leading to significant breaches in confidentiality and integrity. Furthermore, the availability of the service may be compromised if malicious commands disrupt critical networking processes or crash system services. The device itself becomes a pivot point for further attacks against internal assets, enabling lateral movement within the network topology. This scenario aligns with common attack patterns observed in IoT and embedded systems where weak input validation leads to complete host compromise.
From a classification perspective, this vulnerability corresponds directly to CWE-78 Improper Neutralization of Special Elements used in an OS Command commonly known as OS Command Injection. It also relates to CWE-20 Improper Input Validation regarding the failure to verify that user inputs conform to expected formats and constraints before processing. In terms of offensive security frameworks such as MITRE ATT&CK, this exploitation technique falls under T1059 Command and Scripting Interpreter, specifically leveraging OS-native command shells like sh or bash on Linux-based embedded devices. The attack vector is classified as Local with Privileges Required, indicating that while it does not require network exposure to the public internet for direct execution, it poses a high risk if administrative interfaces are accessible within trusted networks where credential theft may occur.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. The primary solution is to apply the latest firmware updates provided by the vendor, which should include patches that enforce strict input validation and parameterized command execution rather than string concatenation for system calls. If patching is not immediately feasible, administrators should restrict access to the web management interface using network segmentation policies, ensuring it is only reachable from trusted administrative subnets. Additionally, changing default credentials and implementing strong password policies reduces the likelihood of credential compromise that could lead to exploitation. Regular audits of configuration settings and monitoring for unusual outbound connections can help detect potential post-exploitation activities early in the attack lifecycle.