CVE-2025-29913: NASA CryptoLib Buffer Overflow Vulnerability

CVE-2025-29913 Overview

A critical heap buffer overflow vulnerability has been identified in NASA's CryptoLib, a software-only solution implementing the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) to secure communications between spacecraft running the core Flight System (cFS) and ground stations. This vulnerability exists in the Crypto_TC_Prep_AAD function and affects CryptoLib versions 1.3.3 and prior.

The vulnerability allows an attacker to trigger a Denial of Service (DoS) or potentially execute arbitrary code (RCE) by providing a maliciously crafted telecommand (TC) frame that causes an unsigned integer underflow. When exploited, the function attempts to access an out-of-bounds memory location, leading to a segmentation fault.

Critical Impact

Successful exploitation could allow attackers to disrupt spacecraft-ground station communications or potentially achieve remote code execution in mission-critical space systems.

Affected Products

• NASA CryptoLib versions 1.3.3 and prior
• CryptoLib commit d3cc420ace96d02a5b7e83d88cbd2e48010d5723 and earlier
• Systems using CCSDS SDLS-EP for spacecraft communications

Discovery Timeline

• 2025-03-17 - CVE CVE-2025-29913 published to NVD
• 2025-05-07 - Last updated in NVD database

Technical Details for CVE-2025-29913

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read) and represents a heap buffer overflow condition. The flaw resides in the Crypto_TC_Prep_AAD function, which is responsible for preparing Additional Authenticated Data (AAD) during telecommand frame processing.

The core issue stems from an incorrect calculation of tc_mac_start_index. When processing telecommand frames, the function computes the MAC (Message Authentication Code) start index without properly validating that the result remains within the bounds of the ingest buffer. A maliciously crafted TC frame with manipulated length values causes an unsigned integer underflow during this calculation.

Since unsigned integers cannot represent negative values, the underflow wraps around to a very large positive number, causing the function to attempt memory access far beyond the allocated buffer boundaries. This triggers a segmentation fault and process crash, achieving Denial of Service. Given the nature of heap buffer overflows, skilled attackers may also be able to craft payloads that achieve arbitrary code execution.

Root Cause

The root cause is improper input validation and unsafe arithmetic operations in the Crypto_TC_Prep_AAD function. The code fails to implement boundary checks before computing tc_mac_start_index, allowing malformed telecommand frames with incorrect length fields to trigger unsigned integer underflow. The absence of defensive programming practices around buffer index calculations creates the exploitable condition.

Attack Vector

The attack can be conducted over the network by sending a specially crafted telecommand (TC) frame to a system running the vulnerable CryptoLib implementation. The attacker does not require authentication or user interaction to exploit this vulnerability. The malicious TC frame must contain length values calculated to trigger the integer underflow when the Crypto_TC_Prep_AAD function processes it.

The exploitation process involves:

1. Crafting a telecommand frame with manipulated length fields
2. Sending the malicious frame to the target system's communication interface
3. The Crypto_TC_Prep_AAD function processes the frame and calculates an invalid tc_mac_start_index
4. The unsigned integer underflow causes out-of-bounds memory access
5. The system crashes (DoS) or potentially executes attacker-controlled code (RCE)

For detailed technical information about the vulnerability, refer to the GitHub Security Advisory.

Detection Methods for CVE-2025-29913

Indicators of Compromise

• Unexpected segmentation faults or crashes in processes using CryptoLib
• Abnormal telecommand frames with inconsistent or suspicious length fields
• Memory corruption indicators in CryptoLib-dependent applications
• Unusual crash patterns in spacecraft communication handling systems

Detection Strategies

• Implement network monitoring to detect malformed telecommand frames with anomalous length values
• Deploy application-level monitoring to detect segmentation faults in CryptoLib processes
• Use memory protection tools and address sanitizers during development and testing
• Monitor system logs for repeated crashes or memory access violations in communication handlers

Monitoring Recommendations

• Enable crash dump analysis for systems running CryptoLib
• Implement input validation logging for all incoming telecommand frames
• Configure alerts for abnormal termination of CryptoLib-dependent services
• Establish baseline communication patterns to identify anomalous telecommand traffic

How to Mitigate CVE-2025-29913

Immediate Actions Required

• Review all systems utilizing NASA CryptoLib versions 1.3.3 and prior for exposure
• Implement network-level filtering to validate telecommand frame structures before processing
• Consider isolating vulnerable systems from untrusted networks where possible
• Monitor the GitHub Security Advisory for official patch releases

Patch Information

As of the last known state, the vulnerability remains present in the CryptoLib repository at commit d3cc420ace96d02a5b7e83d88cbd2e48010d5723. Organizations should monitor the official NASA CryptoLib repository and the GitHub Security Advisory for updates and official patches.

When a patch becomes available, prioritize testing and deployment across all affected systems. Given the critical nature of spacecraft communications, coordinate patching activities with operational schedules and mission requirements.

Workarounds

• Implement additional input validation at the network perimeter to filter malformed TC frames before they reach CryptoLib
• Deploy runtime memory protection mechanisms such as ASLR and stack canaries on systems running CryptoLib
• Restrict network access to telecommand processing interfaces to trusted sources only
• Consider implementing application-level bounds checking as a defensive layer before calling vulnerable functions

# Example: Restrict network access to telecommand interfaces
# Add firewall rules to limit access to trusted ground station IPs only
iptables -A INPUT -p udp --dport <TC_PORT> -s <TRUSTED_GROUND_STATION_IP> -j ACCEPT
iptables -A INPUT -p udp --dport <TC_PORT> -j DROP