CVE-2025-32882

Executive Summary

CVE-2025-32882 exposes a critical cryptographic weakness in goTenna v1 devices (app 5.5.3, firmware 0.25.5). The custom encryption implementation lacks integrity checks, making messages malleable to an attacker with network access. This allows undetected tampering of encrypted payloads, breaking the confidentiality and integrity of communications. With a CVSS score of 5.3 (Medium), the vulnerability is exploitable over adjacent networks without authentication. No public exploit code or patch exists, but the risk is elevated for tactical or operational use cases where goTenna devices are deployed.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary hardware/software ecosystem (goTenna v1). No open-source supply chain component is involved.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Base Score: 5.3 (Medium)
• Attack Vector: Adjacent Network (AV:A) – attacker must be within radio range of the goTenna mesh.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – no authentication needed.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality Impact: Low (C:L) – message content may be altered but not directly read.
• Integrity Impact: Low (I:L) – messages can be modified without detection.
• Availability Impact: None (A:N) – no denial of service.

Threat Level: Medium. Exploitation requires physical proximity but no authentication. The lack of integrity checks enables man-in-the-middle (MITM) attacks on the mesh network.

Deep Dive & Mechanics

The goTenna v1 device uses a custom encryption scheme for over-the-air messages. The vulnerability stems from the absence of any integrity verification mechanism (e.g., HMAC, digital signature, or authenticated encryption). An attacker who can intercept and retransmit messages can modify ciphertext blocks without detection. This is a classic malleability issue (CWE-649).

Technical Details:

• The encryption algorithm is proprietary but likely uses a stream cipher or block cipher in a mode without authentication (e.g., CTR, ECB, or CBC without MAC).
• Without integrity checks, an attacker can flip bits in the ciphertext to alter the decrypted plaintext predictably.
• The attack requires only the ability to receive and transmit on the goTenna mesh frequency (typically 900 MHz ISM band).
• No decryption key is needed; the attacker only needs to modify the ciphertext in transit.

Attack Scenario:

1. Attacker sniffs a goTenna message using a software-defined radio (SDR) tuned to the mesh frequency.
2. Attacker modifies specific bytes in the ciphertext (e.g., to change a command or location data).
3. Attacker retransmits the modified message on the same frequency.
4. Legitimate recipients decrypt the tampered message, accepting it as valid.

Vulnerable vs. Patched Code

No patched version exists. The vulnerable code is in the goTenna app (version 5.5.3) and firmware (0.25.5). The following pseudo-code illustrates the missing integrity check:

Vulnerable (app 5.5.3):

def send_message(plaintext):
    ciphertext = custom_encrypt(plaintext, key)
    # No integrity tag appended
    radio_transmit(ciphertext)

def receive_message(ciphertext):
    plaintext = custom_decrypt(ciphertext, key)
    # No integrity verification
    process(plaintext)

Patched (hypothetical):

def send_message(plaintext):
    ciphertext = custom_encrypt(plaintext, key)
    tag = hmac_sha256(key, ciphertext)
    radio_transmit(ciphertext + tag)

def receive_message(data):
    ciphertext = data[:-32]
    tag = data[-32:]
    if not hmac_verify(key, ciphertext, tag):
        discard()
        return
    plaintext = custom_decrypt(ciphertext, key)
    process(plaintext)

Exploitation & Lab Setup

Red Team

Prerequisites:

• Software-defined radio (e.g., HackRF One, USRP B200) capable of 900 MHz.
• GNU Radio or similar tool to capture and replay goTenna packets.
• Knowledge of the goTenna packet format (proprietary, but can be reverse-engineered).

Exploitation Steps:

1. Reconnaissance: Use an SDR to capture goTenna traffic on 902-928 MHz ISM band.
2. Packet Analysis: Identify encrypted payloads. Since no integrity check exists, any ciphertext modification will be accepted.
3. Bit Flipping: Modify specific bytes in the ciphertext. For example, if the plaintext contains a command like "MOVE_TO: 45.0, -93.0", flipping bits can change coordinates.
4. Replay: Transmit the modified packet on the same frequency with appropriate timing.

Lab Setup:

• Two goTenna v1 devices with app 5.5.3 and firmware 0.25.5.
• One SDR (HackRF One) connected to a laptop running GNU Radio.
• Python script to capture, modify, and replay packets.

Example Python snippet (conceptual):

import numpy as np
from gnuradio import gr, blocks, digital

# Capture packet
packet = capture_packet(freq=915e6)

# Modify bytes (e.g., flip bit 3 of byte 10)
modified_packet = bytearray(packet)
modified_packet[10] ^= 0x08

# Replay
transmit_packet(bytes(modified_packet), freq=915e6)

Blue Team

Detection:

• Monitor for anomalous packet retransmissions or duplicate messages.
• Use spectrum analysis to detect unusual activity on the goTenna frequency.
• Implement network-level anomaly detection for message content changes.

Mitigation:

• Upgrade to goTenna Pro or other devices that support authenticated encryption (e.g., AES-GCM).
• If upgrade is not possible, implement out-of-band integrity checks (e.g., application-level HMAC).
• Restrict physical access to the mesh network area.

Indicators of Compromise (IOCs)

• Network: Unusual retransmissions of identical packets with slight byte differences.
• Radio: Repeated packets with same source ID but different payloads.
• Device: Unexpected behavior or commands executed without user initiation.
• Logs: goTenna app logs showing decryption of malformed ciphertext (if logging enabled).

Detection Engineering

YARA Rule

rule goTenna_Malleable_Ciphertext {
    meta:
        description = "Detects goTenna v1 packets with modified ciphertext (no integrity check)"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-32882"
    strings:
        $magic = { 47 54 31 } // Example goTenna packet header (GT1)
        $no_tag = { 00 00 00 00 } // Placeholder for missing integrity tag
    condition:
        $magic at 0 and #no_tag > 0
}

Sigma Rule

title: goTenna Malleable Encryption Exploitation
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects repeated goTenna packets with modified payloads indicating bit-flipping attack
author: Valters IT
logsource:
    product: goTenna
    service: mesh_network
detection:
    selection:
        packet_count: > 2
        payload_diff: true
    condition: selection
falsepositives:
    - Legitimate retransmissions due to packet loss
level: medium

Suricata Rule

alert tcp any any -> any any (msg:"goTenna Malleable Ciphertext Detected"; flow:to_server; content:"|47 54 31|"; offset:0; depth:3; content:"|00 00 00 00|"; within:4; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate vulnerable devices: Disconnect goTenna v1 from critical networks if possible.
2. Monitor traffic: Use SDR-based monitoring to detect tampering.
3. Apply application-layer integrity: If source code is available, add HMAC to messages.

Long-term Fix:

• Vendor must release a firmware update that implements authenticated encryption (e.g., AES-GCM or ChaCha20-Poly1305).
• Users should migrate to goTenna Pro or alternative devices with built-in integrity checks.

Workaround:

• Use out-of-band verification (e.g., manual confirmation of critical commands).
• Limit the use of goTenna v1 to non-sensitive communications.

Valters IT
DevSecOps & Cyber Threat Intelligence