CVE-2025-32890

Executive Summary

CVE-2025-32890 identifies a critical cryptographic integrity flaw in goTenna Mesh devices running app version 5.5.3 and firmware 1.1.12. The vulnerability stems from the use of a custom encryption implementation that lacks any additional integrity checking mechanisms (e.g., HMAC, digital signatures). This allows an attacker with network-level access to the mesh network to perform a ciphertext malleability attack, modifying encrypted messages in transit without detection. The CVSS score of 5.3 (Medium) reflects the low attack complexity and the potential for data integrity compromise, though confidentiality and availability are not directly impacted. As of this report, no official patch or workaround has been released by goTenna, and no public proof-of-concept (PoC) code is available.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in a proprietary hardware device (goTenna Mesh). The supply chain risk is limited to the device's firmware update mechanism and the trustworthiness of the manufacturer's software development lifecycle.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Adjacent Network (A) – The attacker must be within radio range of the goTenna Mesh network.
• Attack Complexity (AC): Low (L) – No special conditions or race conditions are required.
• Privileges Required (PR): None (N) – No authentication is needed to intercept or modify messages.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): None (N) – The encryption itself is not broken; only integrity is affected.
• Integrity (I): Low (L) – An attacker can modify message content, but cannot inject arbitrary commands or escalate privileges.
• Availability (A): None (N) – No denial-of-service impact.

Threat Level: Medium. The attack requires physical proximity to the mesh network, but the lack of integrity checking makes it feasible for a determined adversary to manipulate communications.

Deep Dive & Mechanics

The goTenna Mesh device uses a custom encryption protocol to secure messages between nodes. The vulnerability arises because the encryption implementation does not include any integrity verification mechanism, such as a Message Authentication Code (MAC) or digital signature. In standard secure communication, encryption alone (e.g., AES-CTR) provides confidentiality but not integrity. Without a MAC, an attacker can perform a bit-flipping attack on the ciphertext, altering the plaintext in predictable ways.

For example, if the plaintext is a command like "MOVE:10", an attacker could flip specific bits in the ciphertext to change it to "MOVE:20". The receiving device will decrypt the modified ciphertext and process the altered command, believing it came from a legitimate source. This is possible because the decryption process does not verify that the ciphertext has not been tampered with.

The attack vector is the mesh network's radio frequency (RF) layer. An attacker with a compatible radio (e.g., a software-defined radio or another goTenna device) can intercept and retransmit modified packets. The lack of integrity checking means the receiver has no way to detect the tampering.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable implementation and the ideal patched version.

Vulnerable Code (Conceptual):

# Vulnerable: Encryption without integrity
def encrypt_message(plaintext, key):
    cipher = AES.new(key, AES.MODE_CTR)
    ciphertext = cipher.encrypt(plaintext)
    return ciphertext

def decrypt_message(ciphertext, key):
    cipher = AES.new(key, AES.MODE_CTR)
    plaintext = cipher.decrypt(ciphertext)
    return plaintext

Patched Code (Conceptual):

# Patched: Encryption with HMAC integrity check
import hmac
import hashlib

def encrypt_message(plaintext, key):
    cipher = AES.new(key, AES.MODE_CTR)
    ciphertext = cipher.encrypt(plaintext)
    mac = hmac.new(key, ciphertext, hashlib.sha256).digest()
    return ciphertext + mac

def decrypt_message(ciphertext_with_mac, key):
    ciphertext = ciphertext_with_mac[:-32]  # Assuming SHA256 HMAC
    mac = ciphertext_with_mac[-32:]
    expected_mac = hmac.new(key, ciphertext, hashlib.sha256).digest()
    if not hmac.compare_digest(mac, expected_mac):
        raise Exception("Integrity check failed")
    cipher = AES.new(key, AES.MODE_CTR)
    plaintext = cipher.decrypt(ciphertext)
    return plaintext

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Two goTenna Mesh devices (victim nodes) with app 5.5.3 and firmware 1.1.12.
2. A third goTenna Mesh device or a software-defined radio (e.g., HackRF One) configured to operate on the same frequency (typically 902-928 MHz ISM band).
3. A laptop with GNU Radio and a custom script to capture and replay packets.

Exploitation Steps:

1. Reconnaissance: Use a spectrum analyzer to identify the goTenna Mesh network frequency.
2. Packet Capture: Use GNU Radio to capture encrypted packets from the air.
3. Bit-Flipping: Identify the target plaintext (e.g., a command or message) and calculate which bits to flip to achieve the desired modification.
4. Replay: Transmit the modified ciphertext back into the mesh network.
5. Verification: Observe that the receiving node processes the modified message without error.

Example Attack Script (Conceptual):

# Red Team: Bit-flipping attack on AES-CTR ciphertext
def bit_flip(ciphertext, original_plaintext, target_plaintext):
    # XOR the ciphertext with the difference between original and target plaintext
    diff = bytes([o ^ t for o, t in zip(original_plaintext, target_plaintext)])
    modified_ciphertext = bytes([c ^ d for c, d in zip(ciphertext, diff)])
    return modified_ciphertext

# Usage
original_pt = b"MOVE:10"
target_pt = b"MOVE:20"
modified_ct = bit_flip(captured_ciphertext, original_pt, target_pt)
transmit(modified_ct)

Blue Team (Defensive)

Detection:

1. Network Monitoring: Deploy RF monitoring tools to detect anomalous packet patterns, such as repeated retransmissions or unexpected command sequences.
2. Integrity Verification: Implement application-layer integrity checks (e.g., digital signatures) on top of the existing encryption, if possible.
3. Anomaly Detection: Use machine learning models to identify deviations from normal message patterns.

Mitigation:

1. Firmware Update: Await an official patch from goTenna that adds integrity checking (e.g., HMAC).
2. Network Segmentation: Isolate goTenna Mesh networks from critical systems.
3. Physical Security: Restrict physical access to the mesh network area to prevent attackers from getting within radio range.

Indicators of Compromise (IOCs)

• Network Traffic: Unusual retransmissions or duplicate packets on the goTenna Mesh frequency (902-928 MHz).
• Device Logs: Logs showing unexpected command execution or messages that do not match expected patterns.
• Firmware Version: Devices running app 5.5.3 and firmware 1.1.12.
• RF Anomalies: Presence of unknown devices transmitting on the same frequency with abnormal signal characteristics.

Detection Engineering

YARA Rule

rule goTenna_Mesh_Integrity_Vulnerability {
    meta:
        description = "Detects goTenna Mesh devices with vulnerable firmware (app 5.5.3, firmware 1.1.12)"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-32890"
    strings:
        $firmware = "1.1.12" ascii wide nocase
        $app = "5.5.3" ascii wide nocase
    condition:
        $firmware or $app
}

Sigma Rule

title: goTenna Mesh Integrity Vulnerability Detection
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation of CVE-2025-32890 via anomalous RF traffic patterns
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: rf_monitor
detection:
    selection:
        frequency: "902-928 MHz"
        packet_type: "goTenna Mesh"
        anomaly: "bit_flip_pattern"
    condition: selection
falsepositives:
    - Legitimate firmware updates
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-32890 goTenna Mesh Integrity Attack"; flow:to_server; content:"|00 01 02 03|"; depth:4; offset:0; classtype:attempted-admin; sid:1000001; rev:1;)

Note: The above Suricata rule is a placeholder. Actual detection would require deep packet inspection of the goTenna protocol, which is proprietary.

Remediation & Mitigation

1. Immediate Action: Disconnect goTenna Mesh devices from any critical networks until a patch is available.
2. Workaround: Implement application-layer integrity checks (e.g., digital signatures) on messages before encryption, if the device's API allows.
3. Vendor Contact: Contact goTenna support to request a firmware update that includes integrity verification (e.g., HMAC-SHA256).
4. Monitoring: Deploy RF monitoring to detect any tampering attempts.
5. User Awareness: Train users to verify message authenticity through out-of-band channels (e.g., voice confirmation).

Valters IT
DevSecOps & Cyber Threat Intelligence Division
Report generated for CVE-2025-32890