Summary
Netgate pfSense CE contains an OS command injection vulnerability in gateway monitoring. An authenticated user with gateway edit privileges may inject shell metacharacters through an IPv6 link-local zone index, potentially causing commands to run as root when the gateway monitor is applied.
Netgate pfSense CE contains an OS command injection vulnerability in gateway monitoring. An authenticated user with gateway edit privileges may inject shell metacharacters through an IPv6 link-local zone index, potentially causing commands to run as root when the gateway monitor is applied.
Affected context
The vulnerability occurs in pfSense CE gateway configuration and monitoring workflows when an administrator with gateway edit privileges can set a Monitor IP using an IPv6 link-local address. The risk exists when the zone index is accepted without adequate validation and is later incorporated into a shell command used by the dpinger monitoring process.
The vulnerability occurs in pfSense CE gateway configuration and monitoring workflows when an administrator with gateway edit privileges can set a Monitor IP using an IPv6 link-local address. The risk exists when the zone index is accepted without adequate validation and is later incorporated into a shell command used by the dpinger monitoring process.
Exploit preconditions
- Attack surface: Gateway configuration and IPv6 monitoring settings
- Required access: An authenticated account with permission to edit gateways
- Trigger point: Applying or activating gateway monitoring configuration
- Why exploitation is possible: The IPv6 link-local zone value is insufficiently validated and is passed into a shell command without appropriate escaping, allowing shell metacharacters to alter command interpretation
- Attack surface: Gateway configuration and IPv6 monitoring settings
- Required access: An authenticated account with permission to edit gateways
- Trigger point: Applying or activating gateway monitoring configuration
- Why exploitation is possible: The IPv6 link-local zone value is insufficiently validated and is passed into a shell command without appropriate escaping, allowing shell metacharacters to alter command interpretation
Why this happens
The underlying flaw is OS command injection caused by combining attacker-influenced configuration data with a shell command. The gateway monitoring code passes an unvalidated IPv6 zone index to the dpinger command, allowing shell syntax embedded in that value to be interpreted by the operating system. This behavior maps to CWE-78: Improper Neutralization of Special Elements used in an OS Command.
The underlying flaw is OS command injection caused by combining attacker-influenced configuration data with a shell command. The gateway monitoring code passes an unvalidated IPv6 zone index to the dpinger command, allowing shell syntax embedded in that value to be interpreted by the operating system. This behavior maps to CWE-78: Improper Neutralization of Special Elements used in an OS Command.
Potential impact
- An attacker could execute arbitrary operating system commands
- Commands could run with root privileges
- The firewall configuration and security controls could be modified
- Sensitive configuration data may be accessed or altered
- The appliance could be used for persistence, disruption, or network pivoting
- An attacker could execute arbitrary operating system commands
- Commands could run with root privileges
- The firewall configuration and security controls could be modified
- Sensitive configuration data may be accessed or altered
- The appliance could be used for persistence, disruption, or network pivoting
General mitigation guidance
Mitigation generally focuses on preventing user-controlled gateway values from becoming shell syntax.
Common defensive patterns include:
- Prefer direct process execution APIs that pass arguments without invoking a shell
- Apply strict allowlist validation to IPv6 addresses and permitted zone-index formats
- Treat gateway configuration values as untrusted input even when entered by authenticated administrators
- Enforce least privilege for monitoring processes and administrative service components
- Add server-side validation before configuration persistence and again before command execution
- Use centralized command-construction controls and security-focused testing for administrative input paths
Mitigation generally focuses on preventing user-controlled gateway values from becoming shell syntax.
Common defensive patterns include:
- Prefer direct process execution APIs that pass arguments without invoking a shell
- Apply strict allowlist validation to IPv6 addresses and permitted zone-index formats
- Treat gateway configuration values as untrusted input even when entered by authenticated administrators
- Enforce least privilege for monitoring processes and administrative service components
- Add server-side validation before configuration persistence and again before command execution
- Use centralized command-construction controls and security-focused testing for administrative input paths
How teams detect issues like this
Detection approaches may include:
- Static analysis rules identifying shell invocation with concatenated or interpolated configuration values
- Code review checks for subprocess or command execution APIs receiving gateway, address, or interface data
- Tests using invalid and metacharacter-containing zone values to verify strict rejection
- Monitoring for unexpected changes to gateway monitor settings and unusual root-level process activity
- Policy enforcement requiring allowlist validation for network identifiers and prohibiting shell-based command construction
- Automated security review tools that flag command execution paths involving administrative input
Detection approaches may include:
- Static analysis rules identifying shell invocation with concatenated or interpolated configuration values
- Code review checks for subprocess or command execution APIs receiving gateway, address, or interface data
- Tests using invalid and metacharacter-containing zone values to verify strict rejection
- Monitoring for unexpected changes to gateway monitor settings and unusual root-level process activity
- Policy enforcement requiring allowlist validation for network identifiers and prohibiting shell-based command construction
- Automated security review tools that flag command execution paths involving administrative input
