CVE-2025-29909: NASA CryptoLib RCE Vulnerability

CVE-2025-29909 Overview

CVE-2025-29909 is a heap buffer overflow vulnerability in NASA's CryptoLib, a software-only solution that implements 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_ApplySecurity() function, where an attacker can craft a malicious Telecommand (TC) frame that causes out-of-bounds memory writes due to an integer underflow (CWE-191).

Critical Impact

This vulnerability can result in denial of service (DoS) or, under certain conditions, remote code execution (RCE) on satellite ground stations and mission control software that process malformed TC frames.

Affected Products

• NASA CryptoLib versions 1.3.3 and prior
• Satellite ground station software using CryptoLib for TC processing
• Mission control systems implementing CCSDS SDLS-EP via CryptoLib

Discovery Timeline

• 2025-03-17 - CVE-2025-29909 published to NVD
• 2025-04-30 - Last updated in NVD database

Technical Details for CVE-2025-29909

Vulnerability Analysis

The vulnerability stems from improper validation of TC frame lengths in the Crypto_TC_ApplySecurity() function. When processing incoming Telecommand frames, CryptoLib fails to properly verify that the frame length (tc_header.fl) is sufficient to contain the mandatory header components (segment header and FECF). This allows an attacker to supply a crafted TC frame with an artificially small frame length value.

The root issue is classified as CWE-191 (Integer Underflow), where arithmetic operations on the frame length produce negative or unexpectedly small values when subtracting the header and trailer sizes. These underflowed values subsequently drive memory operations, causing heap buffer overflows during frame processing.

The network-accessible attack vector means that any system accepting TC frames from untrusted sources without strict pre-validation is vulnerable. Given the nature of space communications infrastructure, successful exploitation could compromise critical mission control operations.

Root Cause

The root cause is an integer underflow vulnerability in frame length calculations. When the tc_header.fl field contains a value smaller than the combined size of TC_FRAME_HEADER_SIZE, segment_hdr_len, and fecf_len, the resulting calculation underflows. This leads to incorrect buffer size computations and subsequent out-of-bounds memory writes during TC frame processing.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker with the ability to inject malformed TC frames into the communication channel can exploit this vulnerability. This is particularly concerning for satellite ground stations or mission control software where network-accessible interfaces process incoming telecommand data.

The attacker crafts a TC frame with a tc_header.fl value that is intentionally too small, causing the length calculation to underflow. When CryptoLib processes this frame, it performs memory operations based on the corrupted length values, writing data beyond allocated heap buffer boundaries.

// Security patch from src/core/crypto_tc.c
// Source: https://github.com/nasa/CryptoLib/commit/c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc
 
    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);

The patch adds a boundary check to verify that the frame length is sufficient before proceeding with frame parsing, returning CRYPTO_LIB_ERR_TC_FRAME_LENGTH_UNDERFLOW if the validation fails.

Detection Methods for CVE-2025-29909

Indicators of Compromise

• Unexpected crashes or restarts of ground station TC processing services
• Memory corruption errors or segmentation faults in CryptoLib-dependent applications
• Anomalous TC frames with unusually small frame length header values
• Heap corruption indicators in system logs from mission control software

Detection Strategies

• Implement network monitoring for malformed CCSDS TC frames with invalid length fields
• Deploy memory safety analysis tools to detect heap overflow attempts in real-time
• Monitor CryptoLib error logs for CRYPTO_LIB_ERR_TC_FRAME_LENGTH_UNDERFLOW status codes (post-patch)
• Use application-layer firewalls to validate TC frame structure before processing

Monitoring Recommendations

• Enable verbose logging in CryptoLib and downstream TC processing applications
• Implement alerting on process crashes or abnormal terminations in ground station software
• Monitor memory utilization patterns for signs of heap corruption or exploitation attempts
• Establish baseline TC frame characteristics to identify statistical anomalies in incoming traffic

How to Mitigate CVE-2025-29909

Immediate Actions Required

• Update CryptoLib to a version containing commit c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc or later
• Audit all systems using CryptoLib for TC processing and prioritize patching
• Implement strict input validation for TC frames at network boundaries before CryptoLib processing
• Consider network segmentation to limit exposure of TC processing endpoints

Patch Information

NASA has released a security patch for this vulnerability. The fix is available in commit c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc on the official CryptoLib GitHub repository. The patch adds proper boundary validation to ensure the TC frame length is sufficient before proceeding with frame processing. Organizations should apply this patch immediately to all affected deployments.

For detailed information, refer to the GitHub Security Advisory and the patch commit.

Workarounds

• Implement pre-processing validation of TC frame lengths before passing to CryptoLib
• Deploy network-level filtering to reject TC frames with frame length values below minimum valid thresholds
• Restrict network access to TC processing endpoints to trusted, authenticated sources only
• Consider running CryptoLib processes in sandboxed environments to limit impact of potential exploitation

# Configuration example - Verify CryptoLib version and apply patch
git clone https://github.com/nasa/CryptoLib.git
cd CryptoLib
git fetch origin c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc
git checkout c7e8a8745ff4b5e9bd7e500e91358e86d5abedcc
# Rebuild and redeploy CryptoLib
make clean && make