CVE-2026-17250 Overview
CVE-2026-17250 is a stack-based buffer overflow vulnerability in the firmware update functionality of the TP-Link TL-MR6400 v7 router. The flaw resides in how the device processes attacker-controlled metadata contained within a firmware image. An authenticated attacker on an adjacent network can supply a crafted firmware image to trigger memory corruption on the stack. Successful exploitation allows arbitrary code execution on the affected device, providing full control over router operations, traffic, and connected clients. The vulnerability is classified under CWE-121: Stack-based Buffer Overflow.
Critical Impact
Authenticated adjacent-network attackers can achieve arbitrary code execution on TL-MR6400 v7 routers by uploading a crafted firmware image, resulting in full device compromise.
Affected Products
- TP-Link TL-MR6400 v7 (firmware update component)
- Router firmware images processed by the update handler on TL-MR6400 v7
- Deployments exposing the administrative interface to adjacent network segments
Discovery Timeline
- 2026-08-21 - CVE-2026-17250 published to NVD
- 2026-08-25 - Last updated in NVD database
Technical Details for CVE-2026-17250
Vulnerability Analysis
The vulnerability exists in the firmware update handler on the TL-MR6400 v7. The handler parses metadata fields embedded in the firmware image without validating their length against the destination stack buffer. When an attacker submits a firmware image containing oversized metadata, the parser copies data beyond the allocated buffer boundary. This overwrites adjacent stack memory, including saved return addresses and local variables. Exploitation requires authenticated access to the router's management interface and adjacent-network reachability, such as Wi-Fi or LAN connectivity. Once memory corruption occurs, an attacker can hijack control flow and execute arbitrary code within the context of the update process, which typically runs with elevated privileges on embedded routers.
Root Cause
The root cause is missing bounds checking during the parsing of attacker-controlled metadata inside firmware image files. The firmware update routine trusts length or size fields declared in the image header rather than enforcing fixed limits tied to the receiving stack buffer. This aligns with the CWE-121 pattern where unsafe copy operations on untrusted input corrupt the call stack.
Attack Vector
The attacker must first authenticate to the router with high privileges, then deliver a crafted firmware image through the update interface from an adjacent network. Because firmware updates typically execute with root privileges on embedded devices, successful exploitation yields code execution at the highest privilege level. The vulnerability does not require user interaction beyond the attacker's own actions.
No verified proof-of-concept code is publicly available. Refer to the TP-Link FAQ #5259 and the TL-MR6400 firmware download page for vendor guidance and updated images.
Detection Methods for CVE-2026-17250
Indicators of Compromise
- Unexpected firmware version strings or build identifiers on TL-MR6400 v7 devices that do not match the vendor's published releases.
- Administrative login events followed by firmware upload attempts from adjacent-network addresses that do not correspond to authorized administrators.
- Router reboots, service restarts, or configuration resets immediately following a firmware update POST request.
Detection Strategies
- Monitor HTTP or HTTPS traffic to the router administrative interface for firmware upload endpoints and inspect uploaded image sizes and headers.
- Alert on firmware update attempts originating from non-management VLANs or unauthorized wireless clients.
- Compare firmware image hashes against vendor-published values before and after any update event.
Monitoring Recommendations
- Forward router syslog and administrative audit logs to a centralized log platform and retain them for post-incident review.
- Track authentication events on the router management interface for brute-force patterns or credential reuse.
- Baseline outbound connections from the router to detect command-and-control activity that would follow successful code execution.
How to Mitigate CVE-2026-17250
Immediate Actions Required
- Apply the fixed firmware for TL-MR6400 v7 published on the TP-Link firmware download portal as soon as it is available for your region.
- Rotate router administrator credentials and enforce strong, unique passwords to reduce the risk of the authenticated prerequisite being met.
- Restrict administrative access to a dedicated management VLAN or wired interface and disable remote management from untrusted networks.
Patch Information
TP-Link publishes updated firmware for the TL-MR6400 v7 through its regional support portals. Consult the TP-Link TL-MR6400 v7 firmware page, the regional firmware page, and TP-Link FAQ #5259 for the correct image and installation instructions. Validate the firmware checksum published by the vendor before applying updates.
Workarounds
- Disable Wi-Fi and unused LAN ports where operationally feasible to reduce adjacent-network exposure until the patched firmware is installed.
- Limit the number of accounts with administrative privileges and audit those accounts for unused or shared credentials.
- Segment the router management interface behind a firewall rule that only permits access from a defined administrative host.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
