CVE-2025-44647

Executive Summary

CVE-2025-44647 exposes a critical design flaw in the TRENDnet TEW-WLC100P wireless LAN controller (firmware version 2.03b03). The device ships with the i_dont_care_about_security_and_use_aggressive_mode_psk option enabled in its strongSwan IPsec configuration. This forces the IKE Responder to accept IKEv1 Aggressive Mode with Pre-Shared Keys (PSK), which transmits the PSK hash in cleartext over the network. An attacker within radio range or on the same network segment can capture this hash and perform offline brute-force or dictionary attacks to recover the PSK, leading to full IPsec tunnel compromise.

Key Risk: The PSK hash is transmitted without any encryption or integrity protection, enabling offline cracking. No patch is currently available from TRENDnet.

Supply Chain & Package Security

This vulnerability is not in an open-source package but in a proprietary embedded firmware. The strongSwan library itself is not vulnerable; the misconfiguration is in the device’s configuration file. Supply chain risk is limited to the device’s firmware distribution channel.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attacker must be able to capture network traffic (e.g., on the same LAN or via wireless sniffing).
• Attack Complexity (AC): Low (L) – No special conditions required; the hash is sent in every IKE Aggressive Mode exchange.
• Privileges Required (PR): None (N) – No authentication needed to trigger the exchange.
• User Interaction (UI): None (N) – The device automatically responds to IKEv1 Aggressive Mode requests.
• Scope (S): Unchanged (U) – The compromise is limited to the IPsec tunnel.
• Confidentiality (C): High (H) – The PSK can be recovered, leading to decryption of all IPsec traffic.
• Integrity (I): None (N) – No direct integrity impact.
• Availability (A): None (N) – No availability impact.

Overall CVSS Score: 7.5 (High)

Threat Level: High – Exploitation is straightforward with widely available tools (e.g., Wireshark, tshark, hashcat, John the Ripper).

Deep Dive & Mechanics

The vulnerability stems from the strongSwan configuration file on the TEW-WLC100P. The option i_dont_care_about_security_and_use_aggressive_mode_psk is a strongSwan-specific flag that, when enabled, allows the IKE Responder to accept IKEv1 Aggressive Mode with PSK authentication.

IKEv1 Aggressive Mode vs. Main Mode:

• Main Mode: Exchanges six messages, protecting the identity and PSK hash. The PSK is never transmitted in cleartext.
• Aggressive Mode: Exchanges only three messages. The initiator sends its identity and a hash of the PSK in the first message. The responder replies with its own hash. This hash is transmitted in cleartext and can be captured.

Attack Flow:

1. Attacker sends an IKEv1 Aggressive Mode initiation packet to the TEW-WLC100P.
2. The device responds with its PSK hash (HASH_R) in the second message.
3. Attacker captures this hash using a packet sniffer.
4. Attacker uses a tool like psk-crack (from strongSwan) or hashcat to perform offline brute-force/dictionary attack on the captured hash.
5. Once the PSK is recovered, the attacker can decrypt all IPsec traffic and potentially impersonate legitimate peers.

Why This Is Dangerous: The option name itself (i_dont_care_about_security_and_use_aggressive_mode_psk) indicates the vendor was aware of the security implications but chose to enable it anyway.

Vulnerable vs. Patched Code

Vulnerable Configuration (TEW-WLC100P 2.03b03):

# /etc/strongswan.conf or similar
charon {
    i_dont_care_about_security_and_use_aggressive_mode_psk = yes
}

Patched Configuration (Hypothetical):

# Remove or set to no
# i_dont_care_about_security_and_use_aggressive_mode_psk = no
# Or better, disable Aggressive Mode entirely:
charon {
    # No aggressive mode allowed
}

Code Difference: The vulnerable configuration explicitly enables the insecure option. A patch would either remove this line or set it to no. Additionally, the device should be configured to use IKEv2 or IKEv1 Main Mode only.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Environment:

• Target: TRENDnet TEW-WLC100P with firmware 2.03b03
• Attacker: Kali Linux machine on the same network segment
• Tools: tshark, strongswan (for psk-crack), hashcat

Step 1: Capture the PSK Hash

# Start packet capture
tshark -i eth0 -w capture.pcap

# Trigger IKE Aggressive Mode exchange (e.g., by initiating a connection)
# Alternatively, wait for a legitimate client to connect

Step 2: Extract the Hash

# Use strongSwan's psk-crack tool to extract hash from pcap
psk-crack capture.pcap
# Output: HASH_R: <hex_hash>

Step 3: Crack the PSK

# Using hashcat (mode 5300 for IKE PSK)
hashcat -m 5300 -a 0 hash.txt /usr/share/wordlists/rockyou.txt

Step 4: Decrypt Traffic

# Once PSK is known, use Wireshark to decrypt IPsec traffic
# Edit -> Preferences -> Protocols -> ISAKMP -> Pre-shared key: <PSK>

Blue Team (Defensive)

Detection:

• Monitor for IKEv1 Aggressive Mode packets (UDP port 500, payload type 4).
• Alert on any device responding to Aggressive Mode requests.

Mitigation:

• If possible, disable Aggressive Mode on the device via configuration.
• Use IKEv2 or IKEv1 Main Mode with certificates instead of PSK.
• Segment the network to limit exposure.

Hunting:

• Search for i_dont_care_about_security_and_use_aggressive_mode_psk in device configurations.
• Look for high volumes of IKE Aggressive Mode packets in network logs.

Indicators of Compromise (IOCs)

• Network:
  • IKEv1 Aggressive Mode packets (UDP 500, payload type 4, exchange type 4).
  • Captured PSK hash in pcap files (hex string of 32+ characters).
• Host:
  • Presence of i_dont_care_about_security_and_use_aggressive_mode_psk = yes in strongSwan config.
  • Log entries: "aggressive mode PSK used" in strongSwan logs.
• File:
  • /etc/strongswan.conf or /etc/strongswan.d/charon.conf containing the insecure option.

Detection Engineering

YARA Rule

rule CVE_2025_44647_Trendnet_Aggressive_PSK {
    meta:
        description = "Detects TRENDnet TEW-WLC100P strongSwan config with aggressive mode PSK enabled"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-44647"
    strings:
        $s1 = "i_dont_care_about_security_and_use_aggressive_mode_psk" ascii wide
        $s2 = "yes" ascii wide
    condition:
        $s1 and $s2
}

Sigma Rule

title: Detection of IKEv1 Aggressive Mode PSK Usage
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects network traffic indicating IKEv1 Aggressive Mode with PSK, as used in CVE-2025-44647
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        app_protocol: 'ike'
        ike_version: '1'
        exchange_type: '4'  # Aggressive Mode
        auth_method: '2'    # Pre-Shared Key
    condition: selection
falsepositives:
    - Legitimate use of IKEv1 Aggressive Mode in controlled environments
level: high

Suricata Rule

alert udp $HOME_NET any -> $EXTERNAL_NET 500 (msg:"CVE-2025-44647 IKEv1 Aggressive Mode PSK Detected"; content:"|04|"; offset:12; depth:1; content:"|02|"; offset:14; depth:1; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Aggressive Mode: If possible, access the device’s configuration and set i_dont_care_about_security_and_use_aggressive_mode_psk = no or remove the line entirely.
2. Use IKEv2 or Main Mode: Configure the device to use IKEv2 or IKEv1 Main Mode with certificates instead of PSK.
3. Network Segmentation: Place the TEW-WLC100P on a separate VLAN with strict access controls.

Long-Term Fix:

• TRENDnet must release a firmware update that removes the insecure option or disables it by default.
• Until a patch is available, consider replacing the device with a secure alternative.

Workaround:

• If PSK must be used, ensure the PSK is strong (long, random) to resist offline cracking.
• Monitor for IKE Aggressive Mode traffic and alert on any occurrence.

Valters IT