Introduction
Remote attackers can achieve code execution on Linksys E1700 routers by exploiting a stack-based buffer overflow in the device's web management interface. Public exploit code is available and the vendor has not released a patch, so this vulnerability is a significant risk to any network segment where these devices are deployed.
Linksys is a well-known brand in consumer and small business networking, with millions of routers and extenders in use globally. The E1700 belongs to its budget-focused E-series and is common in home and small office environments.
Technical Information
CVE-2025-9525 is a stack-based buffer overflow in the setWan function of Linksys E1700 router firmware version 1.0.0.4.003. The vulnerable function is reached through the HTTP endpoint /goform/setWan, which the web management interface uses for WAN configuration.
An attacker triggers the flaw by sending a POST request with oversized values in the DeviceName or lanIp parameters. The setWan function copies these user-supplied values into fixed-size buffers on the stack without proper bounds checking. Remote attackers can then overwrite adjacent stack memory, including the function's return address, and that can lead to arbitrary code execution with root privileges.
Key technical points:
- The endpoint
/goform/setWandoes not require authentication, so exploitation is trivial from any network segment that can reach the device. - The cause is a lack of input validation, combined with the absence of stack protection mechanisms in the firmware.
- Exploit code is publicly available, which lowers the barrier for attackers.
Public sources include no code snippets or detailed memory layouts. The vulnerability is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-121 (Stack-based Buffer Overflow).
Affected Systems and Versions
- Product: Linksys E1700 router
- Firmware version: 1.0.0.4.003
- Only this version is confirmed as affected in public sources
- Vulnerable configuration: Any device exposing the
/goform/setWanendpoint (default in standard deployments)
Vendor Security History
Linksys has a documented pattern of stack-based buffer overflow vulnerabilities across its product lines. Recent examples include:
- CVE-2025-9247: Stack-based buffer overflow in RE series
- CVE-2025-9355: Buffer overflow in scheduleAdd function
- CVE-2025-8819: Buffer overflow in setWan function (RE series)
- CVE-2025-9356: Buffer overflow in inboundFilterAdd function
- CVE-2025-9357: Buffer overflow in langSwitchByBBS function
- CVE-2025-9481: Buffer overflow in setIpv6 function
- CVE-2025-9250: Buffer overflow in setPWDbyBBS function
Linksys has responded poorly to coordinated disclosure, with multiple reports of unresponsiveness and a lack of timely patches. There is currently no evidence of a patch or advisory for CVE-2025-9525.
