CVE-2026-111219 in pfSense CE
Summary
by MITRE • 10/15/2026
Netgate pfSense CE through 2.9.0 contains a newline injection vulnerability in services_pppoe_edit.php that allows privileged users to inject mpd.secret entries via unvalidated username POST fields. Attackers with the PPPoE Server Edit privilege can add a line whose secret begins with '!', making mpd5 run commands as root when a PPPoE client authenticates.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in Netgate pfSense Community Edition versions through 2.9.0 represents a critical server-side request forgery and command injection flaw located within the services_pppoe_edit.php component of the web management interface. This issue stems from insufficient input validation on username fields submitted via POST requests, which allows authenticated users with specific privileges to manipulate internal configuration files. Specifically, the vulnerability enables an attacker to inject newline characters into the mpd.secret file, a critical configuration resource used by the multilink PPP daemon (mpd5) for authenticating Point-to-Point Protocol over Ethernet clients. The core technical flaw lies in the application's failure to sanitize or validate special characters within user-supplied input before writing it to system-level configuration files, thereby violating fundamental principles of secure coding regarding data integrity and boundary enforcement.
From an operational perspective, this vulnerability allows for a significant escalation of privileges when exploited by an attacker possessing the PPPoE Server Edit privilege. By crafting a POST request with a username field containing a newline character followed by a secret value that begins with an exclamation mark (' as shell commands to be executed during the authentication process of incoming PPPoE clients. Consequently, when a legitimate or malicious client attempts to authenticate using credentials crafted by the attacker, the system executes these injected commands with root-level privileges. This mechanism effectively bypasses standard access controls and allows for remote code execution on the underlying operating system without requiring additional exploitation steps beyond initial credential submission.
The impact of this vulnerability is severe as it compromises the integrity and confidentiality of the firewall appliance. An attacker can achieve full control over the pfSense device, potentially leading to complete network compromise, data exfiltration, or use of the device as a pivot point for further attacks against internal infrastructure. This aligns with CWE-94 Improper Control of Generation of Code (Command Injection) and CWE-78 Improper Neutralization of Special Elements used in an OS Command. Furthermore, from a tactical perspective within the MITRE ATT&CK framework, this vulnerability facilitates Initial Access through valid accounts followed by Privilege Escalation via command injection techniques such as T1059 or T1068 depending on the specific execution method employed during authentication.
Mitigation strategies must prioritize immediate patching to version 2.9.1 or later where these input validation checks have been strengthened. In environments where upgrading is not immediately feasible, administrators should restrict access to the PPPoE Server Edit privilege strictly to trusted personnel and consider disabling remote web interface access if possible. Additionally, implementing strict network segmentation for management interfaces can limit exposure. Security monitoring should be enhanced to detect unusual POST requests targeting services_pppoe_edit.php or unexpected modifications to mpd.secret files, which may indicate active exploitation attempts. Regular audits of user privileges assigned within the pfSense administrative console are also recommended to ensure that only necessary users retain high-level configuration rights.