CVE-2025-5851 Overview
CVE-2025-5851 is a buffer overflow vulnerability in the Tenda AC15 router running firmware version 15.03.05.19_multi. The flaw resides in the fromadvsetlanip function within the /goform/AdvSetLanip endpoint handled by the HTTP POST request handler. Attackers can manipulate the lanMask argument to trigger a memory corruption condition classified under [CWE-119]. The vulnerability is exploitable remotely across the network and a public exploit disclosure has been referenced by VulDB. Successful exploitation can compromise confidentiality, integrity, and availability of the affected device.
Critical Impact
Remote attackers can trigger a buffer overflow in the Tenda AC15 web management interface, potentially leading to arbitrary code execution or denial of service on the router.
Affected Products
- Tenda AC15 firmware version 15.03.05.19_multi
- Tenda AC15 hardware revision 1.0
- Devices exposing the /goform/AdvSetLanip HTTP endpoint
Discovery Timeline
- 2025-06-09 - CVE-2025-5851 published to NVD
- 2025-06-09 - Last updated in NVD database
Technical Details for CVE-2025-5851
Vulnerability Analysis
The Tenda AC15 web management interface processes HTTP POST requests through goform handlers. The fromadvsetlanip function processes LAN IP configuration submitted to /goform/AdvSetLanip. The handler copies the user-supplied lanMask parameter into a fixed-size stack buffer without enforcing length boundaries. Submitting an oversized lanMask value overruns the destination buffer and corrupts adjacent stack memory, including saved return addresses.
The vulnerability is classified as a classic buffer overflow under [CWE-119], improper restriction of operations within the bounds of a memory buffer. Because the AC15 firmware runs on a MIPS-based platform without robust exploit mitigations, the corruption can be leveraged to redirect execution flow. The EPSS score of 0.621% places this issue in the 70th percentile of exploitation likelihood.
Root Cause
The root cause is the absence of input length validation on the lanMask POST parameter before it is copied into a fixed-size stack buffer inside fromadvsetlanip. The handler trusts the attacker-supplied length, resulting in stack corruption when input exceeds the allocated buffer.
Attack Vector
An authenticated attacker with low privileges sends a crafted HTTP POST request to /goform/AdvSetLanip containing an oversized lanMask value. The request can be issued over the LAN, or remotely if the management interface is exposed to the WAN. Exploitation requires no user interaction. Refer to the Notion Resource on Tenda AC15 and VulDB Advisory #311597 for technical details on the request structure.
No verified proof-of-concept code is included here. See the linked references for reproduction steps published by the disclosing party.
Detection Methods for CVE-2025-5851
Indicators of Compromise
- HTTP POST requests to /goform/AdvSetLanip containing unusually long lanMask values
- Tenda AC15 routers becoming unresponsive or rebooting unexpectedly after receiving web management traffic
- Unexpected configuration changes to LAN IP settings on AC15 devices
- Outbound connections originating from the router to unfamiliar hosts after web administration activity
Detection Strategies
- Inspect HTTP traffic destined for the router management interface and flag POST bodies where the lanMask field exceeds expected dotted-quad length
- Deploy network IDS signatures targeting requests to /goform/AdvSetLanip containing non-conforming netmask values
- Correlate router reboot events with preceding HTTP administrative traffic
Monitoring Recommendations
- Log all access to the Tenda AC15 web administration interface and alert on requests from non-administrative source addresses
- Monitor firmware version and configuration state on managed AC15 devices for unexpected drift
- Track WAN-side exposure of TCP/80 and TCP/443 on AC15 routers and alert when the management interface becomes reachable externally
How to Mitigate CVE-2025-5851
Immediate Actions Required
- Restrict access to the AC15 web management interface to trusted LAN hosts only and disable WAN-side administration
- Change default administrative credentials to reduce the pool of attackers who satisfy the low-privilege requirement
- Segment AC15 devices away from critical assets until a vendor patch is applied
- Review router logs for prior access to /goform/AdvSetLanip from unexpected sources
Patch Information
At the time of publication, no fixed firmware version has been listed in the NVD entry or referenced advisories. Monitor the Tenda Official Website for security firmware releases addressing the fromadvsetlanip handler. Apply the vendor update as soon as it becomes available.
Workarounds
- Disable remote (WAN) management on the AC15 until a patched firmware is released
- Place the router management VLAN behind an access control list permitting only administrative workstations
- Replace end-of-support AC15 devices with currently maintained hardware where patching timelines are uncertain
- Apply upstream firewall rules dropping inbound HTTP/HTTPS traffic to the router from untrusted networks
# Example iptables rule to restrict access to the router management interface
# Allow only the admin workstation 192.168.1.10 to reach the router at 192.168.1.1
iptables -A FORWARD -s 192.168.1.10 -d 192.168.1.1 -p tcp --dport 80 -j ACCEPT
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 80 -j DROP
iptables -A FORWARD -d 192.168.1.1 -p tcp --dport 443 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
