CVE-2025-9813 Overview
CVE-2025-9813 is a buffer overflow vulnerability in the Tenda CH22 router running firmware version 1.0.0.1. The flaw resides in the formSetSambaConf function within /goform/SetSambaConf. Attackers can trigger the overflow by manipulating the samba_userNameSda argument. The issue is exploitable remotely over the network and a public exploit reference exists, raising the likelihood of opportunistic attacks against exposed devices.
Critical Impact
Remote attackers with low privileges can corrupt memory on affected Tenda CH22 devices, potentially leading to arbitrary code execution or device compromise.
Affected Products
- Tenda CH22 hardware (all units running the affected firmware)
- Tenda CH22 firmware version 1.0.0.1
- Devices exposing the /goform/SetSambaConf web management endpoint
Discovery Timeline
- 2025-09-02 - CVE-2025-9813 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-9813
Vulnerability Analysis
The vulnerability is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw exists in the formSetSambaConf handler exposed through the /goform/SetSambaConf endpoint on the device's HTTP management interface. The handler processes the samba_userNameSda request parameter without enforcing proper length checks before copying the value into a fixed-size memory buffer. An authenticated attacker on the network can send a crafted HTTP request containing an oversized samba_userNameSda value to overwrite adjacent memory. Successful exploitation can corrupt control structures on embedded MIPS or ARM SoCs typical of consumer routers, leading to denial of service or arbitrary code execution within the device's web server context.
Root Cause
The root cause is missing input length validation in the Samba configuration handler. The firmware copies user-supplied data into a stack or heap buffer using unsafe string operations, allowing memory beyond the buffer to be overwritten when input exceeds the expected size.
Attack Vector
Exploitation requires network access to the device's web management interface and low-level authenticated access. An attacker submits a POST request to /goform/SetSambaConf with an oversized samba_userNameSda parameter. The vulnerability does not require user interaction. The exploit details are publicly referenced through VulDB and a GitHub issue, increasing the risk of weaponization.
Refer to the GitHub CVE Issue and VulDB #322140 for technical write-ups describing the parameter handling flaw.
Detection Methods for CVE-2025-9813
Indicators of Compromise
- HTTP POST requests to /goform/SetSambaConf containing abnormally long samba_userNameSda parameter values
- Unexpected reboots, web service crashes, or watchdog resets on Tenda CH22 devices
- Outbound connections from the router to unknown hosts following a Samba configuration request
- Web administration interfaces reachable from untrusted networks or the public internet
Detection Strategies
- Inspect HTTP traffic to embedded device management interfaces and alert on requests where samba_userNameSda exceeds typical username lengths (for example, over 64 bytes)
- Deploy intrusion detection signatures targeting POST requests to /goform/SetSambaConf with oversized form fields
- Correlate device reboot events from syslog with preceding HTTP activity to the Samba configuration endpoint
Monitoring Recommendations
- Forward router syslog and HTTP access logs to a central log platform for anomaly review
- Track devices that expose /goform/ administrative paths to non-management network segments
- Baseline normal management traffic patterns and alert on deviations targeting Tenda CH22 endpoints
How to Mitigate CVE-2025-9813
Immediate Actions Required
- Restrict access to the Tenda CH22 web management interface to trusted management VLANs only
- Disable the Samba/file sharing feature on the router if it is not required for business operations
- Rotate administrative credentials and enforce strong passwords to limit access to authenticated endpoints
- Inventory all Tenda CH22 units and identify devices running firmware 1.0.0.1
Patch Information
No vendor patch is currently referenced in the NVD entry or in available vendor advisories. Monitor the Tenda Official Website for firmware updates addressing CVE-2025-9813. Where no patch is available, treat affected devices as end-of-support and plan for replacement with maintained models.
Workarounds
- Block external access to TCP ports hosting the device's HTTP management service at the perimeter firewall
- Place affected routers behind a network segment that prevents untrusted clients from reaching /goform/SetSambaConf
- Disable the Samba service on the device through the administration UI to remove the vulnerable code path from being reachable
- Replace affected devices with vendor-supported hardware if no firmware update is released
# Configuration example: block access to the router management interface from untrusted subnets
iptables -A INPUT -p tcp --dport 80 -s 0.0.0.0/0 -j DROP
iptables -A INPUT -p tcp --dport 80 -s 10.0.0.0/8 -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
