Introduction
Remote attackers can gain code execution on Linksys RE series range extenders by exploiting a stack-based buffer overflow in the device's remote management interface. This vulnerability impacts a wide range of popular models used to expand Wi-Fi coverage in homes and small businesses. The flaw is trivial to exploit, requires no authentication, and remains unpatched as of publication, leaving many networks at risk.
Linksys is a major player in the consumer and SMB networking market, with millions of devices deployed worldwide. The RE series range extenders are widely used for wireless coverage extension. The company's security track record for embedded firmware has been mixed, with several high-impact vulnerabilities reported in recent years.
Technical Information
CVE-2025-8831 is a stack-based buffer overflow in the remoteManagement function of Linksys RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 range extenders running firmware up to 20250801. The vulnerability is triggered via the /goform/remoteManagement endpoint, specifically through the portNumber parameter. The firmware fails to properly validate the length of portNumber before copying it into a stack-allocated buffer. By sending an HTTP POST request with an excessively long portNumber value, an attacker can overwrite stack memory, including the return address, and execute arbitrary code as the web server process.
The root cause is improper input validation and unsafe memory handling in the embedded C code. This is a classic example of CWE-119 and CWE-121, where untrusted input is copied into a fixed-size buffer without bounds checking. The attack does not require authentication and can be performed remotely if the management interface is exposed.
No vendor patch or mitigation is available as of this writing. The vendor was contacted prior to public disclosure but did not respond.
Proof of Concept
The Proof-of-Concept (PoC) exploit for CVE-2025-8831 targets a stack-based buffer overflow vulnerability in Linksys range extenders, specifically models RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000, with firmware versions up to 20250801. This vulnerability resides in the /goform/remoteManagement endpoint, where the portNumber parameter is susceptible to manipulation.
By sending a specially crafted HTTP request to this endpoint, an attacker can input an excessively long string into the portNumber parameter. This input overflows the allocated buffer on the stack, potentially leading to arbitrary code execution. The exploit can be initiated remotely, allowing unauthenticated attackers to compromise the device without physical access.
The PoC demonstrates that by exploiting this vulnerability, an attacker can execute arbitrary commands on the affected device, effectively gaining control over it. This could lead to unauthorized access to the network, interception of data, or further propagation of malicious activities within the network.
It's important to note that the vendor was contacted regarding this vulnerability but did not respond, leaving the devices unpatched and vulnerable to exploitation.
Affected Systems and Versions
The following Linksys range extenders are affected:
- RE6250 (firmware up to 20250801)
- RE6300 (firmware up to 20250801)
- RE6350 (firmware up to 20250801)
- RE6500 (firmware up to 20250801)
- RE7000 (firmware up to 20250801)
- RE9000 (firmware up to 20250801)
All configurations exposing the /goform/remoteManagement endpoint are vulnerable. Remote management does not need to be enabled for the attack to succeed if the endpoint is accessible.
Vendor Security History
Linksys has a history of memory safety and command injection vulnerabilities in its embedded products, especially in the RE series range extenders. Recent CVEs include multiple buffer overflows and command injection flaws in similar endpoints and parameters. Vendor response to coordinated disclosures has been inconsistent, with several reports of non-responsiveness and delayed patching. Security maturity is considered below industry average for this product line.