CVE-2025-70085: OpenSatKit Buffer Overflow Vulnerability

CVE-2025-70085 Overview

A critical stack buffer overflow vulnerability has been discovered in OpenSatKit 2.2.1, affecting the File Manager application's core file handling functions. The vulnerability exists in the EventErrStr buffer within file.c, where unsafe sprintf calls format filename strings without proper length validation, potentially allowing attackers to execute arbitrary code through specially crafted filenames.

Critical Impact

This stack buffer overflow vulnerability enables remote attackers to potentially achieve arbitrary code execution by exploiting unsafe string formatting operations in satellite ground station software, posing significant risks to space mission operations.

Affected Products

• OpenSatKit version 2.2.1
• File Manager (filemgr) application in OpenSatKit cFS apps
• Systems using FILE_ConcatenateCmd() and ConcatenateFiles() functions

Discovery Timeline

• 2026-02-11 - CVE CVE-2025-70085 published to NVD
• 2026-02-12 - Last updated in NVD database

Technical Details for CVE-2025-70085

Vulnerability Analysis

The vulnerability stems from a classic CWE-121 (Stack-based Buffer Overflow) condition in the OpenSatKit File Manager application. The EventErrStr buffer is allocated with a fixed size of 256 bytes on the stack. When the application processes file operations, it uses sprintf to format filenames including Source1Filename and the return value from FileUtil_FileStateStr() into this buffer.

The critical flaw is the absence of any length validation before the string formatting operation. Given that OS_MAX_PATH_LEN is commonly defined as 64-256 bytes, two filenames combined with constant formatting text can easily exceed the 256-byte buffer capacity. This overflow corrupts adjacent stack memory, potentially overwriting return addresses and enabling control flow hijacking.

Root Cause

The root cause is the use of unbounded sprintf calls without implementing proper safety mechanisms. The code lacks:

1. Input validation on filename lengths before formatting
2. Use of bounded format specifiers such as %.*s to limit string lengths
3. Use of safer alternatives like snprintf with explicit size limits

These unsafe patterns are replicated across multiple functions in file.c, including FILE_ConcatenateCmd() and ConcatenateFiles(), creating multiple exploitation entry points within the same codebase.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can trigger the overflow by:

1. Sending commands to the OpenSatKit File Manager with specially crafted, oversized filenames
2. Targeting the file concatenation operations where multiple filenames are formatted together
3. Exploiting the lack of input sanitization to inject payloads that overflow the stack buffer

The vulnerable code pattern involves formatting two path strings into a fixed-size buffer. When the combined length of Source1Filename, the result of FileUtil_FileStateStr(), and the constant text portions exceeds 256 bytes, the stack buffer overflows. An attacker controlling the filename inputs can craft values that precisely overflow the buffer to overwrite the function's return address, redirecting execution to attacker-controlled shellcode.

For detailed technical analysis, refer to the OpenSatKit File Manager Source Code and the security researcher's analysis.

Detection Methods for CVE-2025-70085

Indicators of Compromise

• Abnormally long filename strings in File Manager command inputs exceeding typical path lengths
• Unexpected crashes or segmentation faults in the filemgr application
• Anomalous network traffic containing oversized path strings targeting OpenSatKit command interfaces
• Evidence of stack smashing detected by system protection mechanisms (if enabled)

Detection Strategies

• Implement network monitoring for command packets containing filenames approaching or exceeding OS_MAX_PATH_LEN boundaries
• Deploy static analysis tools to identify additional unbounded sprintf calls in custom OpenSatKit deployments
• Configure intrusion detection systems to alert on malformed or oversized file operation commands
• Monitor system logs for File Manager application crashes or abnormal terminations

Monitoring Recommendations

• Enable stack canary protections and monitor for stack smashing detection alerts
• Implement command logging for all File Manager operations to establish baseline behavior
• Deploy memory corruption detection tools such as AddressSanitizer in development and testing environments
• Monitor ground station communication channels for anomalous command patterns

How to Mitigate CVE-2025-70085

Immediate Actions Required

• Review and audit all OpenSatKit 2.2.1 deployments for exposure to untrusted network inputs
• Implement network segmentation to restrict access to OpenSatKit command interfaces
• Apply input validation at the application boundary to reject filenames exceeding safe length thresholds
• Consider deploying application-level firewalls to filter malicious command inputs

Patch Information

No official vendor patch has been identified at this time. Organizations should monitor the OpenSatKit GitHub Repository for security updates and patch releases. The vulnerable code is located in the File Manager application at cfs/apps/filemgr/fsw/src/file.c.

To remediate the vulnerability, replace all unbounded sprintf calls with snprintf and implement proper length checking on all filename inputs before formatting operations. All instances of the vulnerable pattern in FILE_ConcatenateCmd(), ConcatenateFiles(), and related functions require modification.

Workarounds

• Implement strict input validation to reject filenames exceeding 100 bytes before they reach vulnerable functions
• Deploy Address Space Layout Randomization (ASLR) and stack canaries to increase exploitation difficulty
• Restrict network access to OpenSatKit command interfaces using firewall rules
• Consider recompiling OpenSatKit with compiler hardening flags such as -fstack-protector-strong and -D_FORTIFY_SOURCE=2

# Example: Compile with stack protection enabled
gcc -fstack-protector-strong -D_FORTIFY_SOURCE=2 -o file.o -c file.c

# Example: Network isolation using iptables to restrict command interface access
iptables -A INPUT -p tcp --dport <COMMAND_PORT> -s <TRUSTED_IP_RANGE> -j ACCEPT
iptables -A INPUT -p tcp --dport <COMMAND_PORT> -j DROP