CVE-2025-67858: Foomuuri Argument Injection Vulnerability

CVE-2025-67858 Overview

CVE-2025-67858 is an Improper Neutralization of Argument Delimiters vulnerability (CWE-88) discovered in Foomuuri, a firewall management tool. This vulnerability allows attackers to manipulate the JSON configuration passed to the nft (nftables) command, potentially leading to integrity loss of the firewall configuration or further unspecified impact.

The flaw exists due to insufficient validation of argument delimiters in configuration data before it is processed by the underlying nftables firewall framework. This type of vulnerability, also known as argument injection, occurs when an application fails to properly neutralize special elements that could be interpreted as argument delimiters by downstream components.

Critical Impact

Attackers with local access can manipulate firewall configurations through argument delimiter injection, potentially compromising network security controls and system integrity.

Affected Products

• Foomuuri versions prior to 0.31

Discovery Timeline

• 2026-01-07 - openSUSE publishes security blog post regarding Foomuuri authorization issues
• 2026-01-08 - CVE-2025-67858 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-67858

Vulnerability Analysis

This vulnerability stems from improper handling of argument delimiters within Foomuuri's JSON configuration processing pipeline. When Foomuuri processes configuration data and passes it to the nft command for firewall rule management, it fails to adequately sanitize or neutralize special characters that could be interpreted as argument separators or control characters.

The local attack vector means an attacker must have some level of access to the target system to exploit this vulnerability. Once exploited, the attacker can achieve significant integrity impact by modifying firewall rules, potentially opening unauthorized network access or disabling security controls. The vulnerability also carries confidentiality and availability implications, though these are less severe than the integrity impact.

Root Cause

The root cause is CWE-88: Improper Neutralization of Argument Delimiters in a Command. Foomuuri does not properly escape or validate JSON configuration input before constructing commands for the nft utility. This allows specially crafted configuration values containing argument delimiter characters to be interpreted as separate arguments or commands by the underlying shell or nftables processor.

When user-controlled data containing delimiter characters (such as spaces, quotes, semicolons, or other shell metacharacters) is incorporated into command-line arguments without proper sanitization, the argument boundaries become ambiguous, allowing injection of malicious arguments.

Attack Vector

The attack requires local access to the system where Foomuuri is installed. An attacker can craft malicious JSON configuration data containing specially formatted argument delimiters that, when processed by Foomuuri and passed to nft, result in unintended command execution or configuration manipulation.

The attack flow involves:

1. Identifying Foomuuri's JSON configuration input mechanism
2. Crafting JSON values containing argument delimiter characters
3. Submitting the malicious configuration through Foomuuri's interface
4. The improperly sanitized data is passed to nft, which interprets the injected delimiters
5. Firewall rules are modified according to the attacker's injected arguments

For technical details on the vulnerability mechanism, refer to the openSUSE Security Blog Post.

Detection Methods for CVE-2025-67858

Indicators of Compromise

• Unexpected modifications to firewall rules or nftables configurations
• Anomalous JSON configuration entries in Foomuuri logs containing special characters or escape sequences
• Unauthorized changes to network access policies without corresponding administrative actions
• Unusual nft command invocations with malformed or unexpected arguments in system logs

Detection Strategies

• Monitor Foomuuri configuration files and logs for suspicious JSON payloads containing delimiter characters such as semicolons, backticks, or shell metacharacters
• Implement file integrity monitoring on nftables rule files and Foomuuri configuration directories
• Review system audit logs for unexpected nft command executions, particularly those with unusual argument patterns
• Deploy endpoint detection rules to alert on process chains where Foomuuri spawns nft with anomalous command-line arguments

Monitoring Recommendations

• Enable verbose logging in Foomuuri to capture all configuration changes and command invocations
• Implement real-time alerting for any modifications to firewall rules outside of authorized change windows
• Correlate Foomuuri activity logs with D-Bus authorization events to identify potential exploitation attempts
• Establish baseline firewall configurations and alert on any deviations

How to Mitigate CVE-2025-67858

Immediate Actions Required

• Update Foomuuri to version 0.31 or later immediately to address this vulnerability
• Review current firewall configurations for any unauthorized or unexpected rules that may indicate prior exploitation
• Restrict local access to systems running Foomuuri to authorized administrators only
• Audit recent configuration changes for signs of argument injection attempts

Patch Information

The vulnerability is addressed in Foomuuri version 0.31. Organizations should upgrade to this version or later to remediate CVE-2025-67858. For detailed information, consult the SUSE Bugzilla CVE-2025-67858 tracking entry and the openSUSE Security Blog Post.

Workarounds

• Restrict local system access to minimize the attack surface until patching is complete
• Implement strict access controls on Foomuuri configuration interfaces and D-Bus endpoints
• Deploy application-level input validation for any systems interfacing with Foomuuri
• Consider temporarily disabling Foomuuri and using direct nftables management if the risk is deemed unacceptable

# Check current Foomuuri version
foomuuri --version

# Update Foomuuri on openSUSE/SUSE systems
sudo zypper update foomuuri

# Verify firewall rules integrity after update
sudo nft list ruleset