Introduction
Remote attackers can take full control of Linksys E1700 routers running firmware 1.0.0.4.003 by exploiting a stack-based buffer overflow in the device's web interface. This vulnerability (CVE-2025-9527) is actively discussed in the security community due to the availability of public exploits and the lack of vendor response. For organizations and individuals relying on Linksys E1700 for network connectivity, this issue exposes critical infrastructure to remote code execution risks.
About Linksys: Linksys is a well-known manufacturer of consumer and small business networking hardware, with millions of devices deployed globally. Their product line includes routers, range extenders, and mesh systems. The E1700 is a value-focused wireless router popular in home and small office environments. Linksys has faced multiple security challenges in recent years, with several buffer overflow vulnerabilities reported in 2025 alone.
Technical Information
CVE-2025-9527 is a stack-based buffer overflow in the QoSSetup function of Linksys E1700 firmware version 1.0.0.4.003. The vulnerability is triggered when the router's web interface receives a crafted HTTP POST request to /goform/QoSSetup with an oversized ack_policy parameter. The firmware fails to validate the length of this parameter before copying it into a stack-allocated buffer, leading to memory corruption on the stack.
This flaw allows remote attackers to overwrite the return address or other control data on the stack, potentially achieving arbitrary code execution with the privileges of the web server process. The vulnerability is similar in nature to other 2025 Linksys buffer overflows (such as CVE-2025-9392 and CVE-2025-9393), which also stem from insufficient input validation in web interface functions. The affected firmware does not implement modern exploit mitigations like stack canaries or ASLR, making exploitation more straightforward.
No official patch is available from Linksys as of the publication date. The vendor has not responded to coordinated disclosure attempts.
Proof of Concept
The proof-of-concept (PoC) for this vulnerability demonstrates how an attacker can exploit the NTP configuration interface of the affected Linksys devices to execute arbitrary commands. By manipulating specific parameters within the NTP configuration, such as manual_year_select, manual_month_select, manual_day_select, manual_hour_select, manual_min_select, and manual_sec_select, an attacker can inject and execute OS commands.
For instance, by sending a crafted HTTP request to the /goform/NTP endpoint with malicious payloads in these parameters, the device processes the input without proper validation, leading to command execution. This vulnerability allows remote attackers to gain unauthorized access and potentially take full control of the device.
It's important to note that while the PoC provides a clear method for exploitation, executing such attacks without authorization is illegal and unethical. This information is intended solely for educational purposes and to aid in the development of appropriate security measures.
PoC Reference:
Detection Methods
Detecting vulnerabilities in network devices like the Linksys E8450 v1.2.00.360516 requires a multifaceted approach. While specific detection methods for this particular vulnerability are not detailed in the provided sources, we can outline general strategies to identify such issues:
1. Network Traffic Analysis:
Monitoring network traffic for unusual patterns can reveal exploitation attempts. For instance, unexpected outbound connections or irregular data flows may indicate a compromise. Tools like Zeek (formerly Bro) can be instrumental in this analysis. An example of Zeek's application is its use in detecting CVE-2020-16898, where specific scripts were developed to identify malicious activities associated with that vulnerability. (github.com)
2. Log File Examination:
Regularly reviewing system and application logs can help identify unauthorized access or configuration changes. Look for anomalies such as failed login attempts, changes to system files, or unexpected system reboots.
3. Vulnerability Scanning:
Utilizing automated tools to scan devices for known vulnerabilities is crucial. These scanners compare device configurations against databases of known issues, flagging potential security gaps.
4. Firmware Integrity Checks:
Regularly verifying the integrity of device firmware ensures that no unauthorized modifications have occurred. This can be achieved through checksums or cryptographic hashes provided by the vendor.
5. Behavioral Analysis:
Implementing systems that monitor device behavior for deviations from the norm can be effective. For example, if a router begins to communicate with unfamiliar external servers, it may indicate a compromise.
By integrating these methods into a comprehensive security strategy, organizations can enhance their ability to detect and respond to vulnerabilities in network devices.
Detection Reference:
Affected Systems and Versions
- Product: Linksys E1700 Wireless Router
- Firmware: 1.0.0.4.003
- Only this firmware version is confirmed affected. Other Linksys products, including RE series range extenders, have similar but distinct vulnerabilities.
- The vulnerability is present when the web interface is accessible, especially if exposed to untrusted networks.
Vendor Security History
- Multiple stack-based buffer overflows reported in Linksys products in 2025, including CVE-2025-9392 and CVE-2025-9393.
- Vendor has a history of not responding to coordinated disclosure or releasing timely patches for critical issues.
- No official advisory or patch for CVE-2025-9527 as of the publication date.