CVE-2026-17252: TP-Link TL-MR6400 v7 Router DoS Vulnerability

CVE-2026-17252 Overview

CVE-2026-17252 is a stack-based out-of-bounds write vulnerability in the login request handling functionality of the administrative web interface on TP-Link TL-MR6400 v7 routers. An unauthenticated attacker on an adjacent network can trigger the flaw by sending a specially crafted malformed HTTP request to the web management interface.

Successful exploitation crashes the web service process. The result is a denial-of-service condition and temporary loss of access to the router's web management interface. The weakness is classified under CWE-787: Out-of-bounds Write.

Critical Impact
An adjacent unauthenticated attacker can crash the router's web management service using a single malformed HTTP login request, disrupting administration of the device.

Affected Products

TP-Link TL-MR6400 v7 router
TP-Link TL-MR6400 v7 administrative web interface
TP-Link TL-MR6400 v7 firmware versions prior to the vendor fix

Discovery Timeline

2026-08-21 - CVE-2026-17252 published to the National Vulnerability Database (NVD)
2026-08-21 - Last updated in NVD database

Technical Details for CVE-2026-17252

Vulnerability Analysis

The defect resides in the login request handler exposed by the router's administrative web interface. The handler processes HTTP login requests but fails to validate the length or structure of attacker-controlled input before writing it to a stack buffer. This produces a stack-based out-of-bounds write, corrupting adjacent stack memory and destabilizing the web service process.

Because the vulnerable code path is reachable prior to authentication, no valid credentials are required. An attacker only needs network reachability to the router's LAN or wireless segment. The observed impact is a service crash rather than remote code execution, yielding a denial-of-service outcome.

Stack-based out-of-bounds writes on embedded devices frequently degrade device availability and can, depending on protections such as stack canaries and non-executable memory, escalate to memory-corruption primitives. TP-Link's advisory describes the confirmed impact as a crash of the web service.

Root Cause

The root cause is improper bounds checking in the login request parser. Input from a malformed HTTP request is copied into a fixed-size stack buffer without enforcing size constraints, allowing data to overflow the buffer boundary and write outside the intended region.

Attack Vector

The attack vector is Adjacent Network. An unauthenticated attacker positioned on the same broadcast domain as the router — for example, a connected Wi-Fi client or a host on the LAN — sends a crafted HTTP request to the administrative web interface. No user interaction is required.

No verified public proof-of-concept code is available. The vulnerability is described in prose by the vendor advisory; see the TP-Link Support FAQ #5259 for technical details.

Detection Methods for CVE-2026-17252

Indicators of Compromise

Unexpected crash or restart of the router's HTTP administration service (httpd or equivalent) shortly after receiving inbound HTTP traffic.
Loss of access to the web management interface while the device otherwise continues to route traffic.
Malformed or oversized HTTP login POST requests observed against the router's management IP from LAN or wireless clients.

Detection Strategies

Inspect network telemetry from LAN and wireless segments for HTTP requests targeting the router management interface with abnormal Content-Length, header sizes, or login body fields.
Correlate router availability alerts with concurrent HTTP traffic from adjacent hosts to identify probable exploitation attempts.
Alert on repeated web management service restarts, which indicate crash-loop conditions consistent with CWE-787 exploitation.

Monitoring Recommendations

Restrict and log access to the router administrative interface, forwarding logs to a centralized SIEM for correlation.
Monitor DHCP and wireless association logs to identify unauthorized adjacent devices capable of reaching the management interface.
Track firmware version inventory across managed TP-Link devices to confirm patch state for TL-MR6400 v7 units.

How to Mitigate CVE-2026-17252

Immediate Actions Required

Apply the latest TL-MR6400 v7 firmware from the TP-Link download page as soon as it is available.
Disable remote management on the WAN interface and restrict LAN-side administrative access to trusted management hosts.
Segment untrusted Wi-Fi clients onto an isolated guest network that cannot reach the router management IP.

Patch Information

TP-Link addresses this vulnerability through a firmware update for the TL-MR6400 v7 platform. Refer to the TP-Link TL-MR6400 v7 Firmware page and the TP-Link Support FAQ #5259 for the fixed firmware version and installation guidance. Regional builds are also published on the TP-Link Taiwan firmware page.

Workarounds

Restrict administrative interface access to a dedicated management VLAN or a single trusted host until patched firmware is installed.
Enforce strong Wi-Fi authentication (WPA2/WPA3) and rotate pre-shared keys to reduce the pool of adjacent attackers.
Enable rate limiting or firewall rules that drop malformed HTTP requests to the router management IP, where supported.

bash

# Configuration example: restrict router admin access from a Linux management host
# Replace 192.0.2.1 with the router IP and eth0 with the management interface
iptables -A OUTPUT -o eth0 -d 192.0.2.1 -p tcp --dport 80 -m owner --uid-owner root -j ACCEPT
iptables -A OUTPUT -o eth0 -d 192.0.2.1 -p tcp --dport 80 -j DROP