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. With public exploit code available and no patch from the vendor, this vulnerability presents a significant risk to any network segment where these devices are deployed.
Linksys is a widely recognized brand in consumer and small business networking, with millions of routers and extenders in use globally. The E1700 model is part of their budget-focused E-series, commonly found in home and small office environments.
Technical Information
CVE-2025-9525 is a stack-based buffer overflow vulnerability in the setWan function of the Linksys E1700 router firmware version 1.0.0.4.003. The vulnerability is exposed via the HTTP endpoint /goform/setWan, which is used for WAN configuration through the device's web management interface.
The flaw is triggered when an attacker sends a POST request with oversized values in the DeviceName or lanIp parameters. The setWan function copies these user-supplied parameters into fixed-size buffers on the stack without proper bounds checking. This allows remote attackers to overwrite adjacent stack memory, including the function's return address, which can lead to arbitrary code execution with root privileges.
Key technical points:
- The endpoint
/goform/setWandoes not require authentication, making exploitation trivial from any reachable network segment. - The vulnerability is caused by lack of input validation and absence of stack protection mechanisms in the firmware.
- Exploit code is publicly available, lowering the barrier for attackers.
No code snippets or detailed memory layouts are included in public sources, but 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
Vendor response to coordinated disclosure has been poor, with multiple reports of unresponsiveness and lack of timely patches. There is no evidence of a patch or advisory for CVE-2025-9525 at this time.