CVE-2026-5476: NASA cFS Buffer Overflow Vulnerability

CVE-2026-5476 Overview

An integer overflow vulnerability has been identified in NASA Core Flight System (cFS) up to version 7.0.0 when running on 32-bit platforms. The vulnerability exists in the CFE_TBL_ValidateCodecLoadSize function within the file cfe/modules/tbl/fsw/src/cfe_tbl_passthru_codec.c. This flaw allows an attacker with adjacent network access and low-level privileges to manipulate input data, triggering an integer overflow condition that could compromise data integrity and availability.

Critical Impact

Exploitation of this integer overflow in NASA's flight software framework could affect table management operations, potentially leading to corrupted configuration data or unexpected behavior in embedded space systems.

Affected Products

• NASA cFS (Core Flight System) versions up to 7.0.0
• Deployments running on 32-bit architectures
• Systems utilizing the table passthrough codec functionality

Discovery Timeline

• 2026-04-03 - CVE-2026-5476 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2026-5476

Vulnerability Analysis

The vulnerability resides in the table validation codec component of NASA's Core Flight System, a reusable flight software framework designed for spacecraft missions. The affected function, CFE_TBL_ValidateCodecLoadSize, is responsible for validating the size of table data during codec load operations. On 32-bit systems, improper handling of size calculations can result in an integer overflow condition.

When table data with carefully crafted size parameters is processed, the validation function may incorrectly calculate buffer boundaries due to integer wraparound. This can lead to subsequent operations working with invalid memory boundaries, potentially causing data corruption or system instability. The attack requires adjacent network access, making remote exploitation challenging but possible in network-connected ground station or spacecraft communication scenarios.

Root Cause

The root cause is classified under CWE-189 (Numeric Errors), specifically involving integer overflow in size validation logic. The vulnerability occurs because the function performs arithmetic operations on size values without adequate bounds checking to prevent overflow on 32-bit integer types. When the input size exceeds the maximum representable value for a 32-bit integer, the calculation wraps around to a smaller value, bypassing intended validation constraints.

Attack Vector

The attack vector requires adjacent network access, meaning the attacker must have access to the local network segment or communication link where the cFS instance operates. The attacker needs low-level privileges to submit table data through the system's table management interface. By providing specially crafted size parameters in table load requests, an attacker can trigger the integer overflow condition.

The exploitation complexity is high due to several factors:

• The attacker must have precise knowledge of the target system's memory layout
• Timing and specific system state conditions must align
• Adjacent network access limits the attack surface significantly

The vulnerability affects confidentiality, integrity, and availability at a limited level, as successful exploitation could allow reading or modifying small amounts of data, or causing localized service disruptions in the table management subsystem.

Detection Methods for CVE-2026-5476

Indicators of Compromise

• Abnormal table load operations with unusually large or negative size parameters in cFS logs
• Unexpected memory allocation failures or corruption errors in the cfe_tbl_passthru_codec.c module
• System crashes or resets originating from the table management service
• Anomalous network traffic targeting table management endpoints from adjacent network sources

Detection Strategies

• Monitor cFS telemetry and logs for table validation errors or unexpected size values during load operations
• Implement network intrusion detection rules to identify suspicious table management commands from unexpected sources
• Deploy integrity monitoring on critical table configuration files to detect unauthorized modifications
• Review system event logs for patterns indicating repeated failed or malformed table load attempts

Monitoring Recommendations

• Enable verbose logging for the CFE_TBL module to capture detailed validation outcomes
• Establish baseline metrics for normal table operations and alert on statistical anomalies
• Monitor memory utilization patterns for unexpected spikes or allocation failures in table processing
• Configure alerts for authentication failures or unauthorized access attempts to table management interfaces

How to Mitigate CVE-2026-5476

Immediate Actions Required

• Assess whether your cFS deployment operates on 32-bit architectures and uses the affected table passthrough codec functionality
• Review network access controls to limit adjacent network access to trusted systems only
• Implement additional input validation at the application layer for table size parameters
• Monitor the GitHub Issue #954 for patch release announcements

Patch Information

A fix is planned for an upcoming version milestone of the NASA cFS project. Organizations should monitor the official GitHub cFS Repository for patch releases. Additional details about the vulnerability are available through VulDB Vulnerability #355080.

Until an official patch is released, organizations should implement the recommended workarounds and closely monitor their deployments for signs of exploitation attempts.

Workarounds

• Restrict network access to cFS table management interfaces using network segmentation and access control lists
• Implement application-level input validation to reject table load requests with size parameters approaching 32-bit integer boundaries
• Consider migrating affected deployments to 64-bit architectures where feasible to eliminate the 32-bit integer overflow condition
• Deploy additional monitoring and logging around table operations to detect potential exploitation attempts

# Example: Network access restriction for cFS table management (iptables)
# Restrict table management port access to trusted hosts only
iptables -A INPUT -p udp --dport 1235 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p udp --dport 1235 -j DROP