CVE-2025-9361: Linksys RE6250 Buffer Overflow Vulnerability

CVE-2025-9361 Overview

CVE-2025-9361 is a stack-based buffer overflow vulnerability affecting multiple Linksys range extender models, including the RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000. The flaw resides in the ipRangeBlockManageRule function reachable through the /goform/ipRangeBlockManageRule endpoint. Attackers can manipulate the ipRangeBlockRuleName, scheduleIp, or ipRangeBlockRuleIpAddr parameters to overflow a fixed-size stack buffer. The exploit details are publicly available, and Linksys did not respond to disclosure attempts, leaving affected devices without an official patch.

Critical Impact
Remote attackers with low-privileged access can trigger a stack buffer overflow on Linksys range extenders, potentially achieving arbitrary code execution or device crash on unpatched firmware.

Affected Products

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

Discovery Timeline

2025-08-23 - CVE-2025-9361 published to the National Vulnerability Database
2025-09-02 - Last updated in NVD database

Technical Details for CVE-2025-9361

Vulnerability Analysis

The vulnerability is a classic stack-based buffer overflow [CWE-119] in the web management interface of multiple Linksys range extenders. The ipRangeBlockManageRule handler in /goform/ipRangeBlockManageRule copies user-supplied HTTP parameter values into fixed-size stack buffers without enforcing length validation. Attackers who submit overlong values for ipRangeBlockRuleName, scheduleIp, or ipRangeBlockRuleIpAddr overwrite adjacent stack memory, including saved return addresses and frame pointers. The exploit has been published on GitHub, increasing the likelihood of opportunistic attacks against exposed devices.

Root Cause

The root cause is the absence of bounds checking when the ipRangeBlockManageRule function processes IP range block rule parameters. The handler relies on unsafe string copy operations that trust the length of attacker-controlled request fields. Because these range extenders use a MIPS-based embedded Linux platform with limited exploit mitigations, overwriting saved registers on the stack can redirect execution flow to attacker-controlled data.

Attack Vector

The vulnerability is reachable over the network through the device's HTTP administration interface. An attacker needs authenticated access at a low privilege level to invoke the /goform/ipRangeBlockManageRule endpoint. Where administrative web access is exposed to untrusted networks, or where default credentials remain in place, the barrier to exploitation drops considerably. Successful exploitation impacts confidentiality, integrity, and availability of the device.

The vulnerability manifests when the ipRangeBlockManageRule handler copies the ipRangeBlockRuleName, scheduleIp, or ipRangeBlockRuleIpAddr parameters into a fixed-size stack buffer without length validation. See the GitHub Vulnerability Documentation and the public proof-of-concept for the request structure and overflow offsets.

Detection Methods for CVE-2025-9361

Indicators of Compromise

HTTP POST requests to /goform/ipRangeBlockManageRule containing abnormally long values in the ipRangeBlockRuleName, scheduleIp, or ipRangeBlockRuleIpAddr parameters.
Unexpected reboots, web interface crashes, or service hangs on Linksys RE-series range extenders.
New outbound connections from range extender management IPs to unfamiliar external hosts, suggesting post-exploitation activity.

Detection Strategies

Inspect web traffic destined for Linksys range extenders for requests to /goform/ipRangeBlockManageRule and flag payloads exceeding expected parameter lengths.
Correlate device reboot events with preceding HTTP requests to identify likely exploitation attempts.
Use network segmentation telemetry to identify range extenders communicating outside expected management subnets.

Monitoring Recommendations

Enable syslog forwarding from range extenders, where supported, and ingest logs into your SIEM for centralized analysis.
Monitor for repeated POST requests to /goform/ endpoints from a single source IP within short time windows.
Track firmware version inventory across Linksys RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 devices to ensure ongoing visibility.

How to Mitigate CVE-2025-9361

Immediate Actions Required

Restrict access to the device's web administration interface to trusted management VLANs only and disable remote (WAN-side) administration.
Change default and weak administrative credentials to reduce the likelihood of an authenticated attacker reaching the vulnerable endpoint.
Identify all Linksys RE6250, RE6300, RE6350, RE6500, RE7000, and RE9000 devices on the network and isolate them from sensitive segments.
Consider replacing end-of-life range extenders with currently supported hardware, given the vendor's lack of response to disclosure.

Patch Information

No official patch is available from Linksys at the time of publication. According to the disclosure record, the vendor was contacted early but did not respond. Defenders should treat affected firmware versions 1.0.013.001, 1.0.04.001, 1.0.04.002, 1.1.05.003, and 1.2.07.001 as unpatched and apply compensating controls. Monitor the Linksys support site for any future firmware updates addressing this issue.

Workarounds

Block external access to the administrative web interface using upstream firewall rules.
Place range extenders on an isolated management network with no direct access from user or guest subnets.
Disable the IP range block feature if it is not actively used in the deployment.
Decommission affected devices in favor of supported hardware where feasible.

bash

# Example upstream firewall rule to block WAN access to the management interface
# Replace <extender_ip> with the device address and <mgmt_subnet> with your trusted range
iptables -A FORWARD -p tcp -d <extender_ip> --dport 80 ! -s <mgmt_subnet> -j DROP
iptables -A FORWARD -p tcp -d <extender_ip> --dport 443 ! -s <mgmt_subnet> -j DROP