CVE-2025-9357: Linksys RE6250 Buffer Overflow Vulnerability

CVE-2025-9357 Overview

CVE-2025-9357 is a stack-based buffer overflow vulnerability affecting multiple Linksys range extender products, including the RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000. The flaw resides in the langSwitchByBBS function handler at /goform/langSwitchByBBS, where the langSelectionOnly parameter is processed without proper bounds checking. Attackers can exploit this issue remotely over the network to corrupt stack memory. According to the disclosure, the exploit is publicly available, and the vendor did not respond to early disclosure attempts. The vulnerability is classified under CWE-119, Improper Restriction of Operations within the Bounds of a Memory Buffer.

Critical Impact

Remote attackers can trigger memory corruption on affected Linksys range extenders, potentially leading to arbitrary code execution or device crash, with public exploit code available and no vendor patch released.

Affected Products

• Linksys RE6250 firmware 1.0.04.001, RE6350 firmware 1.0.04.001
• Linksys RE6300 firmware 1.2.07.001, RE6500 firmware 1.0.013.001
• Linksys RE7000 firmware 1.1.05.003, RE9000 firmware 1.0.04.002

Discovery Timeline

• 2025-08-23 - CVE-2025-9357 published to NVD
• 2025-09-02 - Last updated in NVD database

Technical Details for CVE-2025-9357

Vulnerability Analysis

The vulnerability resides in the web management interface of affected Linksys range extenders. The langSwitchByBBS function processes HTTP requests sent to the /goform/langSwitchByBBS endpoint and reads the langSelectionOnly parameter from the request. The handler copies this user-supplied value into a fixed-size stack buffer without validating its length. Sending an oversized value overflows the buffer and overwrites adjacent stack data, including saved return addresses. This memory corruption pattern is characteristic of [CWE-119] flaws common in embedded MIPS and ARM router firmware.

Root Cause

The root cause is the absence of bounds checking when copying the attacker-controlled langSelectionOnly argument into a stack-allocated buffer inside langSwitchByBBS. The firmware likely uses unsafe C library functions such as strcpy or sprintf rather than length-bounded equivalents. Because the affected binaries lack modern mitigations such as stack canaries and address space layout randomization, return address overwrites translate directly into control-flow hijacking opportunities.

Attack Vector

Exploitation requires network access to the device's HTTP management interface and low-privilege credentials. An attacker submits a crafted POST request to /goform/langSwitchByBBS containing an oversized langSelectionOnly payload. Successful exploitation can crash the httpd service or yield arbitrary code execution in the context of the web daemon, typically running as root on consumer routers. Public proof-of-concept material referenced in the disclosure documents the request structure and payload offsets. See the GitHub PoC for Vulnerability for technical details.

Detection Methods for CVE-2025-9357

Indicators of Compromise

• HTTP POST requests to /goform/langSwitchByBBS containing abnormally long langSelectionOnly parameter values.
• Unexpected restarts or crashes of the device httpd process and loss of management interface availability.
• New outbound connections from Linksys range extenders to unfamiliar external hosts following management interface access.

Detection Strategies

• Inspect network traffic destined for range extender management interfaces for oversized request bodies targeting /goform/ endpoints.
• Deploy intrusion detection signatures that flag HTTP requests where the langSelectionOnly parameter exceeds reasonable length thresholds.
• Correlate authentication events on Linksys devices with subsequent crashes or reboots that may indicate exploitation attempts.

Monitoring Recommendations

• Forward syslog and SNMP trap data from network infrastructure into a centralized logging platform for anomaly review.
• Track administrative authentication failures and successes on consumer-grade networking equipment within the corporate or remote-worker environment.
• Alert on outbound connections originating from network appliances that historically communicate only with vendor cloud services.

How to Mitigate CVE-2025-9357

Immediate Actions Required

• Restrict access to the device's web management interface to trusted local network segments and block exposure to the internet.
• Disable remote management features on affected RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 devices.
• Change default and weak administrative credentials, since exploitation requires low-privilege authenticated access.
• Inventory deployed Linksys range extenders and evaluate replacement with currently supported hardware.

Patch Information

No vendor patch is available at the time of disclosure. According to the advisory, Linksys was contacted early but did not respond. Several affected models are end-of-life consumer products that may not receive future firmware updates. Refer to the Linksys Official Site for product lifecycle status and the VulDB #321060 Detail entry for tracking updates.

Workarounds

• Place affected range extenders behind a network firewall that blocks inbound HTTP and HTTPS traffic to the management interface.
• Segment IoT and consumer networking equipment onto a dedicated VLAN isolated from production assets and sensitive data stores.
• Replace unsupported or end-of-life Linksys range extenders with current models that receive ongoing firmware updates.
• Monitor traffic to and from the device for indicators of post-exploitation activity and unauthorized configuration changes.