CVE-2025-29909

Executive Summary

CVE-2025-29909 is a critical heap buffer overflow vulnerability in CryptoLib, a software library implementing the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) for securing spacecraft communications. The flaw resides in the Crypto_TC_ApplySecurity() function, allowing an attacker to craft a malicious Telecommand (TC) frame that triggers out-of-bounds memory writes. This can lead to denial of service (DoS) or, under specific conditions, remote code execution (RCE). The vulnerability affects versions 1.3.3 and prior. A patch is available via the referenced commit. No public proof-of-concept (PoC) or exploit code has been identified at this time.

Supply Chain & Package Security

CryptoLib is a critical component in the space communications supply chain, used in conjunction with NASA's core Flight System (cFS). Compromise of this library could allow an attacker to inject malicious commands into a spacecraft's command stream, potentially leading to loss of control or data exfiltration. Organizations using CryptoLib must verify they are using the patched version and implement strict input validation for all incoming TC frames.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder. Based on the vulnerability description, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N) – The attacker can send malicious TC frames over the network.
• Attack Complexity (AC): Low (L) – Crafting a malicious frame requires no special conditions.
• Privileges Required (PR): None (N) – No authentication needed to send frames.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component is the only one affected.
• Confidentiality (C): High (H) – Potential for RCE could lead to data exfiltration.
• Integrity (I): High (H) – RCE could allow command injection.
• Availability (A): High (H) – DoS is a direct consequence.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Estimated Score: 9.8 (Critical)

Threat Level: Critical. The vulnerability is remotely exploitable with no authentication, and the impact includes both DoS and potential RCE in a highly sensitive domain (spacecraft communications).

Deep Dive & Mechanics

The vulnerability is a classic heap buffer overflow in the Crypto_TC_ApplySecurity() function. This function is responsible for applying security measures to Telecommand (TC) frames as per the CCSDS SDLS-EP standard. The flaw occurs when parsing a maliciously crafted TC frame that contains a length field or data structure that is not properly validated.

Root Cause: The function likely copies user-supplied data into a heap-allocated buffer without verifying that the size of the incoming data does not exceed the allocated buffer size. An attacker can manipulate the frame's length fields to cause a write beyond the buffer's boundaries.

Attack Vector: An attacker with network access to a ground station or spacecraft that uses CryptoLib can inject a specially crafted TC frame. The frame is processed by Crypto_TC_ApplySecurity(), which triggers the overflow.

Impact:

• Denial of Service (DoS): Overwriting critical heap metadata or adjacent memory can cause the application to crash.
• Remote Code Execution (RCE): By carefully controlling the overflowed data, an attacker may overwrite function pointers or other critical data structures to redirect execution flow to arbitrary code.

Vulnerable vs. Patched Code

The patch is available at commit c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc. While the exact code diff is not provided, the fix likely involves adding bounds checking before memory copy operations in Crypto_TC_ApplySecurity().

Vulnerable Code (Conceptual):

void Crypto_TC_ApplySecurity(TC_Frame *frame) {
    uint8_t *buffer = malloc(MAX_FRAME_SIZE);
    // No bounds check on frame->data_length
    memcpy(buffer, frame->data, frame->data_length);
    // ... further processing
}

Patched Code (Conceptual):

void Crypto_TC_ApplySecurity(TC_Frame *frame) {
    if (frame->data_length > MAX_FRAME_SIZE) {
        // Handle error
        return;
    }
    uint8_t *buffer = malloc(MAX_FRAME_SIZE);
    memcpy(buffer, frame->data, frame->data_length);
    // ... further processing
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A test environment running CryptoLib version 1.3.3 or earlier.
• Network access to the service processing TC frames.
• Understanding of the CCSDS TC frame structure.

Exploitation Steps:

1. Craft a Malicious TC Frame: Create a TC frame with an oversized data length field. For example, set the length to a value larger than the expected maximum (e.g., 0xFFFF).
2. Send the Frame: Transmit the frame to the target service.
3. Trigger the Overflow: The Crypto_TC_ApplySecurity() function will attempt to copy the oversized data into a fixed-size heap buffer, causing a heap buffer overflow.
4. Achieve RCE (Advanced): To achieve RCE, the attacker would need to carefully craft the overflow data to overwrite a function pointer or return address. This requires knowledge of the target's memory layout and heap allocator behavior.

Example Payload (Conceptual):

import socket

# Craft a malicious TC frame
frame = b'\x01\x02\x03\x04'  # Header
frame += b'\xFF\xFF'          # Oversized length field (65535 bytes)
frame += b'A' * 65535         # Payload to overflow

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(frame, ('target_ip', 1234))

Blue Team (Defense & Detection)

Detection:

• Monitor for TC frames with abnormally large length fields.
• Use heap integrity checks (e.g., glibc's MALLOC_CHECK_ environment variable) to detect heap corruption.
• Implement network-based intrusion detection rules (see Suricata rule below).

Mitigation:

• Apply the patch immediately.
• Implement strict input validation for all TC frames before processing.
• Use address space layout randomization (ASLR) and non-executable heap (NX) to make exploitation harder.

Indicators of Compromise (IOCs)

• Network IOCs:
  • TC frames with length fields exceeding the maximum allowed size (e.g., > 1024 bytes for typical frames).
  • Repeated connection attempts from a single IP to the TC processing service.
• Host IOCs:
  • Application crashes or segmentation faults in processes using CryptoLib.
  • Heap corruption errors in system logs.
  • Unexpected memory allocations or deallocations.

Detection Engineering

YARA Rule

rule CVE_2025_29909_CryptoLib_HeapOverflow {
    meta:
        description = "Detects heap buffer overflow in CryptoLib TC frames"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-29909"
    strings:
        $s1 = "Crypto_TC_ApplySecurity" ascii wide nocase
        $s2 = "TC" ascii wide nocase
    condition:
        $s1 and $s2
}

Sigma Rule

title: Detection of Malicious TC Frame with Oversized Length
id: cve-2025-29909-cryptolib-tc-overflow
status: experimental
description: Detects network traffic containing TC frames with oversized length fields targeting CryptoLib
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        - payload_length: "> 1024"
        - payload_content: "|FF FF|"  # Example oversized length field
    condition: selection
falsepositives:
    - Legitimate large TC frames (rare)
level: high

Suricata Rule

alert udp any any -> any any (msg:"CVE-2025-29909 CryptoLib TC Heap Overflow Attempt"; content:"|FF FF|"; offset:4; depth:2; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Patch: Apply the commit c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc to CryptoLib.
2. Input Validation: Implement strict validation of all TC frame fields, especially length fields, before processing.
3. Network Segmentation: Isolate ground station networks from untrusted networks.
4. Monitoring: Deploy the provided detection rules to identify exploitation attempts.
5. Least Privilege: Run CryptoLib processes with minimal necessary privileges.
6. Regular Updates: Subscribe to CryptoLib security advisories for future patches.

Valters IT