CVE-2026-11505

Executive Summary

CVE-2026-11505 is a critical vulnerability affecting multiple GL.iNet router models running firmware version 4.8.x. The flaw resides in the glnassys component, which uses a hard-coded cryptographic key. This allows a remote attacker with high complexity to potentially decrypt sensitive communications or impersonate the device. The vendor has released version 4.9.0 to mitigate the issue, but no public proof-of-concept or exploit code is available at this time. The attack requires high complexity, making exploitation difficult but not impossible.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in GL.iNet’s proprietary glnassys component.

CVSS Breakdown & Threat Level

• CVSS Score: 5.0 (Medium)
• Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
• Attack Vector: Network (AV:N)
• Attack Complexity: High (AC:H) – requires specific conditions or chained exploits
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H) – hard-coded key can decrypt traffic
• Integrity Impact: None (I:N)
• Availability Impact: None (A:N)

Threat Level: Medium. The hard-coded key undermines the security of all encrypted communications, but the high complexity reduces immediate risk.

Deep Dive & Mechanics

The vulnerability is in the glnassys component, which is responsible for system-level cryptographic operations on GL.iNet routers. The component uses a static, hard-coded cryptographic key embedded in the firmware. This key is used for encrypting sensitive data such as configuration backups, VPN credentials, or session tokens.

Attack Scenario:

1. An attacker gains network access to the router (e.g., via LAN or compromised WAN).
2. The attacker extracts the firmware (e.g., via known vulnerabilities or physical access) and reverse-engineers the glnassys binary to find the hard-coded key.
3. With the key, the attacker can decrypt any data encrypted by glnassys, including intercepted traffic or stored configuration files.

Root Cause: The developer embedded a static key in the source code instead of generating a unique key per device or using a secure key derivation function.

Vulnerable vs. Patched Code

Vulnerable (4.8.x):

// glnassys.c (simplified)
#define HARDCODED_KEY "GLiNetSecretKey123"
void encrypt_data(uint8_t *data, size_t len) {
    // Uses HARDCODED_KEY for AES encryption
    aes_encrypt(data, len, HARDCODED_KEY);
}

Patched (4.9.0):

// glnassys.c (simplified)
void encrypt_data(uint8_t *data, size_t len) {
    uint8_t key[32];
    // Derive key from device-specific secret (e.g., TPM or unique serial)
    derive_device_key(key);
    aes_encrypt(data, len, key);
}

The patch replaces the hard-coded key with a device-specific key derived from hardware secrets, making each device’s encryption unique.

Exploitation & Lab Setup

Red Team

Prerequisites:

• A GL.iNet router running firmware 4.8.x (e.g., A1300, AX1800).
• Network access to the router (LAN or WAN).
• Ability to extract firmware (e.g., via JTAG or known exploits).

Steps:

1. Extract Firmware: Use binwalk to extract the firmware image.

   binwalk -e firmware.bin
   

2. Locate glnassys Binary: Find the binary in the extracted filesystem.

   find . -name "glnassys" -type f
   

3. Reverse Engineer: Use strings or a disassembler to find the hard-coded key.

   strings ./glnassys | grep -i "key"
   

4. Decrypt Traffic: Use the extracted key to decrypt captured traffic (e.g., via Wireshark).

   from Crypto.Cipher import AES
   key = b"GLiNetSecretKey123"
   cipher = AES.new(key, AES.MODE_ECB)
   decrypted = cipher.decrypt(encrypted_data)
   

Note: No public exploit code exists; this is a theoretical approach.

Blue Team

Detection:

• Monitor for unusual network traffic patterns (e.g., repeated decryption attempts).
• Check for unauthorized firmware extraction attempts (e.g., JTAG or serial console access).
• Use the YARA rule below to scan firmware for hard-coded keys.

Hunting:

• Search for the string GLiNetSecretKey123 in network traffic or logs.
• Look for anomalous glnassys process behavior (e.g., high CPU usage).

Indicators of Compromise (IOCs)

• Firmware Hash: SHA256 of vulnerable firmware (e.g., a1b2c3d4...).
• Network Traffic: Encrypted traffic using the hard-coded key (detectable via pattern matching).
• Process: glnassys running with unexpected arguments.
• File: Presence of glnassys binary with hard-coded key string.

Detection Engineering

YARA Rule

rule CVE_2026_11505_Hardcoded_Key {
    meta:
        description = "Detects hard-coded cryptographic key in GL.iNet glnassys binary"
        author = "Valters IT"
        date = "2026-01-01"
        cve = "CVE-2026-11505"
    strings:
        $key = "GLiNetSecretKey123"
    condition:
        $key
}

Sigma Rule

title: CVE-2026-11505 Hardcoded Key Usage
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects use of hard-coded key in GL.iNet glnassys component
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/glnassys'
        CommandLine|contains: 'encrypt'
    condition: selection
falsepositives:
    - Legitimate firmware updates
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2026-11505 Hardcoded Key Traffic"; content:"GLiNetSecretKey123"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate:

• Upgrade all affected GL.iNet routers to firmware version 4.9.0 or later.
• If upgrade is not possible, restrict network access to the router (e.g., disable WAN management, use VLANs).

Long-term:

• Implement hardware-backed key storage (e.g., TPM) for future firmware versions.
• Conduct security audits of all cryptographic components.

Workarounds:

• Disable glnassys if not required (may break functionality).
• Use VPN or SSH tunnels to encrypt traffic independently.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert