CVE-2026-2877:

Security Advisory: Critical Buffer Overflow in Tenda A18 Routers

Overview

A critical security vulnerability has been identified in certain Tenda A18 wireless routers. The flaw resides in the device’s web management interface (the HTTP daemon or httpd service). Specifically, it is located in a function that handles Wi-Fi security settings. Due to improper coding, an attacker can send a specially crafted network request that overflows a memory buffer on the device, potentially allowing them to take control of the router.

Vulnerability Details

The vulnerability is a stack-based buffer overflow in the /goform/WifiExtraSet function. In simple terms, the software uses an unsafe method (strcpy) to copy user-supplied data for the 5GHz Wi-Fi password encryption setting (wpapsk_crypto5g) into a fixed-size memory buffer without checking the length. By sending a password string that is excessively long, an attacker can overwrite critical memory structures. This can crash the device (causing a denial of-service) or, more critically, allow the execution of arbitrary malicious code. The attack can be launched remotely over the network without prior authentication.

Impact

If successfully exploited, this high-severity vulnerability could allow an attacker to:

• Remotely compromise the router, gaining full administrative control.
• Intercept or redirect network traffic, enabling eavesdropping on sensitive data like login credentials.
• Use the router as a foothold to attack other devices on the local network.
• Render the router inoperable (brick it) through a crash. The public disclosure of exploit details increases the risk of active attacks.

Affected Products

• Tenda A18 router, firmware version 15.13.07.13. Other firmware versions may also be vulnerable.

Remediation and Mitigation

Immediate Action Required:

1. Check for Firmware Updates: Immediately log into your Tenda A18 web administration panel and check for a firmware update. Apply any available update from the official Tenda website. If a fixed version (later than 15.13.07.13) is provided, install it.
2. If No Update is Available: As a critical workaround, disable remote administration (WAN access) to the router’s management interface. Ensure the admin panel is only accessible from your local area network (LAN).
3. Network Segmentation: Consider isolating sensitive devices on a separate network segment until a patch can be applied.
4. Monitor for Announcements: Watch the official Tenda security channel or vendor announcements for a patched firmware release. Plan to apply it as soon as it is available.

Note: There is no effective mitigation that allows keeping the vulnerable feature enabled safely. Patching or strong network access controls are essential.