CVE-2026-67979: NASA cFS Incorrect Access Control Allows Arbitrary Code Execution

Executive Summary

A critical access control vulnerability (CVE-2026-67979) has been disclosed in NASA's core Flight System (cFS) v7.0.1. Incorrect access controls in the Executive Services (ES) dynamic application start path allow an attacker with write access to the target storage medium to execute arbitrary code by placing a malicious shared object (.so) file.

CVSS Score: 9.1 (Critical)

cFS is NASA's open-source, portable flight software framework used in spacecraft, satellites, and ground support systems. This vulnerability carries significant implications for safety-critical and space systems where code integrity is paramount.

Vulnerability Overview

Affected Versions

Technical Analysis

NASA's core Flight System (cFS) is a modular software framework designed for flight and ground applications. The Executive Services (ES) component manages application lifecycle, including the dynamic loading of applications at runtime from the filesystem.

The vulnerability lies in the dynamic application start path: when cFS ES is configured to load applications dynamically, it does not properly validate the integrity or origin of the shared object (.so) files it loads. An attacker who can write to the target storage can plant a malicious .so, which is then loaded and executed by ES during the application start sequence.

Attack Flow

1. Attacker gains write access to the target storage medium
   (e.g., mission data drive, RAM filesystem, network-mounted storage)
2. Attacker places a crafted malicious .so file in the cFS application load path
3. cFS Executive Services dynamically loads the .so during application start
4. Malicious code executes in the context of the cFS process
5. Full code execution achieved within the flight system environment

Deployment Context

cFS runs on:

While a full remote exploitation scenario requires an existing write-access foothold, the absence of code signing or integrity verification on loaded modules means that any party with storage write access can escalate to full code execution — a significant violation of the principle of least privilege in safety-critical systems.

Impact

Immediate Remediation

Step 1: Apply the NASA/cFS Patch

Check the official cFS repository for security patches addressing CVE-2026-67979:

# Clone or update the cFS repository
git clone https://github.com/nasa/cFS.git
cd cFS
git fetch --tags
git log --oneline | head -20   # Review recent commits for security fixes
 
# Check the NASA security advisory for the patched version

Step 2: Restrict the Application Load Path

Limit which directories cFS ES will load applications from, and restrict write permissions:

# Set the cFS app load path to a read-only, integrity-protected directory
chmod 555 /path/to/cfs/apps/
chown root:root /path/to/cfs/apps/
 
# Remove write access for the cFS runtime user
setfacl -m u:cfs-runtime:rx /path/to/cfs/apps/

Step 3: Implement Module Integrity Verification

Until a vendor fix is available, implement a wrapper or pre-load hook that verifies .so signatures before loading:

# Example: verify SHA-256 hashes of all .so files before starting cFS
cat /etc/cfs/app-hashes.sha256
sha256sum --check /etc/cfs/app-hashes.sha256 || { echo "Integrity check failed"; exit 1; }

Consider integrating IMA (Integrity Measurement Architecture) on Linux targets to enforce kernel-level code signing for loaded modules.

Step 4: Audit for Existing Compromise

# List all .so files in the cFS app load path with their modification times
find /path/to/cfs/apps/ -name "*.so" -ls | sort -k8,9
 
# Verify checksums against known-good baseline
sha256sum /path/to/cfs/apps/*.so > /tmp/current-hashes.txt
diff /etc/cfs/baseline-hashes.txt /tmp/current-hashes.txt
 
# Check for unexpected processes or network connections from the cFS PID
lsof -p $(pgrep -x core-cpu1) 2>/dev/null

Broader Context: Security in Space Systems

CVE-2026-67979 highlights a recurring challenge in space and safety-critical software: code that was originally designed for isolated, controlled environments is increasingly deployed in networked or shared-storage contexts. The security assumptions of early cFS versions — that only trusted operators have storage access — no longer hold in modern multi-mission operations centers and cloud-connected ground systems.

Key security principles for cFS deployments:

1. Code signing — All dynamically loaded applications must be signed and verified before execution.
2. Least privilege — The cFS runtime process should have read-only access to the application load path.
3. Integrity monitoring — Continuous integrity measurement of loaded modules.
4. Network segmentation — cFS ground support systems must not be internet-accessible.

Detection Indicators

References

• NVD — CVE-2026-67979
• NASA cFS GitHub Repository
• CWE-284: Improper Access Control
• NASA cFS Documentation

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