CVE-2025-29912: NASA CryptoLib Buffer Overflow Vulnerability

CVE-2025-29912 Overview

CVE-2025-29912 is an integer underflow vulnerability 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. The vulnerability exists in the Crypto_TC_ProcessSecurity function, where an unsigned integer underflow leads to a heap buffer overflow when processing malicious Telecommand (TC) packets.

Critical Impact

This vulnerability allows remote attackers to cause denial of service or potentially achieve remote code execution by sending crafted TC packets with a frame length field set to 0, causing the frame length to be interpreted as 65535 and resulting in out-of-bounds memory access.

Affected Products

• NASA CryptoLib versions 1.3.3 and prior
• Systems running the CCSDS Space Data Link Security Protocol implementation
• Spacecraft running core Flight System (cFS) using CryptoLib for ground station communications

Discovery Timeline

• 2025-03-17 - CVE-2025-29912 published to NVD
• 2025-05-07 - Last updated in NVD database

Technical Details for CVE-2025-29912

Vulnerability Analysis

The vulnerability resides in the Crypto_TC_ProcessSecurity function within CryptoLib's TC packet processing module. When a Telecommand (TC) packet is received with the fl (frame length) field set to 0, the function performs arithmetic operations that result in an unsigned integer underflow. Since unsigned integers cannot represent negative values, the underflow causes the frame length to wrap around to 65535 (the maximum value for a 16-bit unsigned integer).

This corrupted frame length value is subsequently used in memory operations, causing the function to attempt reading or writing beyond the allocated buffer boundaries. The out-of-bounds memory access can corrupt adjacent heap memory structures, potentially allowing an attacker to overwrite critical data or function pointers.

Root Cause

The root cause is the absence of proper validation for the frame length field before performing arithmetic calculations. The Crypto_TC_ProcessSecurity function calculates buffer sizes by subtracting header sizes, segment header length, and FECF (Frame Error Control Field) length from the frame length value. When the input frame length is zero or smaller than the combined size of these headers, the subtraction results in an integer underflow.

The vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), both of which stem from the underlying integer underflow condition.

Attack Vector

An attacker can exploit this vulnerability remotely over a network by sending a specially crafted TC packet to a system running the vulnerable CryptoLib implementation. The attack requires:

1. Network access to the target system processing TC packets
2. The ability to send malformed packets with the fl field set to 0
3. No authentication or user interaction required

The security patch introduces proper validation to prevent the underflow condition:

 
    Crypto_TC_Calc_Lengths(&fecf_len, &segment_hdr_len);
 
+    if(tc_sdls_processed_frame->tc_header.fl <= TC_FRAME_HEADER_SIZE - segment_hdr_len - fecf_len + 1)
+    {
+        status = CRYPTO_LIB_ERR_TC_FRAME_LENGTH_UNDERFLOW;
+        mc_if->mc_log(status);
+        return status;
+    }
+
    // Parse & Check FECF
    Crypto_TC_Parse_Check_FECF(ingest, len_ingest, tc_sdls_processed_frame);

Source: GitHub Commit ca39cb96f21e76102aefb956d2c8c0ba0bd143ca

Detection Methods for CVE-2025-29912

Indicators of Compromise

• Unusual memory consumption or heap corruption signatures in systems running CryptoLib
• TC packets with frame length (fl) field values of 0 or values smaller than the minimum valid frame size
• Crash dumps or core files from Crypto_TC_ProcessSecurity function failures
• Anomalous heap allocation patterns indicating buffer overflow attempts

Detection Strategies

• Implement network traffic monitoring to detect TC packets with invalid frame length values (fl=0 or abnormally small values)
• Deploy memory protection mechanisms such as heap canaries and ASLR to detect and mitigate exploitation attempts
• Monitor system logs for CRYPTO_LIB_ERR_TC_FRAME_LENGTH_UNDERFLOW error codes (after patching)
• Use static analysis tools to identify vulnerable CryptoLib versions in deployed systems

Monitoring Recommendations

• Establish baseline metrics for TC packet processing to identify anomalous packet patterns
• Configure alerts for application crashes or memory violations in CryptoLib-dependent processes
• Monitor for repeated connection attempts with malformed TC packets that could indicate active exploitation
• Review system integrity through periodic memory and heap validation checks

How to Mitigate CVE-2025-29912

Immediate Actions Required

• Update CryptoLib to a version that includes the security patch (commit ca39cb96f21e76102aefb956d2c8c0ba0bd143ca)
• Implement input validation at network boundaries to filter TC packets with zero or invalid frame length values
• Restrict network access to systems processing TC packets to authorized ground stations only
• Enable heap protection mechanisms (ASLR, stack canaries, heap guards) on systems running CryptoLib

Patch Information

NASA has released a security patch addressing this vulnerability. The fix adds explicit validation of the frame length field before performing size calculations, returning an error status CRYPTO_LIB_ERR_TC_FRAME_LENGTH_UNDERFLOW when the frame length is insufficient to contain the required headers.

For detailed patch information, refer to the GitHub Security Advisory GHSA-3f5x-r59x-p8cf and the official commit.

Workarounds

• If immediate patching is not possible, implement external validation to reject TC packets with fl values of 0 or below minimum thresholds
• Deploy network-level filtering to block malformed TC packets before they reach vulnerable CryptoLib instances
• Isolate systems running vulnerable CryptoLib versions from untrusted network segments
• Consider running CryptoLib in a sandboxed environment with restricted memory access permissions

# Example: Update CryptoLib from source with security patch
git clone https://github.com/nasa/CryptoLib.git
cd CryptoLib
git checkout ca39cb96f21e76102aefb956d2c8c0ba0bd143ca
# Build and deploy according to your system requirements
make
make install