CVE-2026-8664 Overview
CVE-2026-8664 is an OS command injection vulnerability in the Rapid7 InsightConnect Finger Plugin on Linux. The flaw exists in the plugin's shell command construction logic, where the user and host parameters are concatenated into a system command without adequate sanitization. Authenticated attackers can inject arbitrary shell metacharacters into these parameters to execute commands in the context of the plugin process. The issue is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command).
Critical Impact
Authenticated attackers can execute arbitrary OS commands on the host running the Finger Plugin, leading to integrity compromise of the InsightConnect orchestration environment.
Affected Products
- Rapid7 InsightConnect Finger Plugin (Linux deployments)
- InsightConnect orchestration workflows that invoke the Finger Plugin
- Downstream automation pipelines consuming Finger Plugin output
Discovery Timeline
- 2026-06-25 - CVE CVE-2026-8664 published to NVD
- 2026-06-25 - Last updated in NVD database
Technical Details for CVE-2026-8664
Vulnerability Analysis
The Finger Plugin wraps the legacy finger utility to query user information on remote hosts. When an InsightConnect workflow triggers the plugin, the supplied user and host parameters are passed into a shell command string that is executed by the underlying operating system. Because the plugin does not neutralize shell metacharacters such as ;, &&, |, backticks, or $(), an authenticated user with workflow execution privileges can break out of the intended command structure.
Exploitation requires authenticated access to InsightConnect with permission to run or modify Finger Plugin steps. Successful injection executes arbitrary commands with the privileges of the plugin runtime, which typically operates inside a container or orchestration host with access to credentials and connected systems.
The attack vector is network-based, and the impact is concentrated on integrity, with secondary effects on confidentiality and availability of the plugin host and any reachable infrastructure.
Root Cause
The root cause is unsafe shell command construction. The plugin builds the finger invocation by interpolating user-controlled strings directly into a shell-interpreted command rather than passing arguments as a list to a non-shell execution function. This pattern allows shell metacharacters in the user or host fields to be parsed and executed by the shell.
Attack Vector
An authenticated attacker submits a Finger Plugin action with a crafted host parameter such as example.com; <arbitrary command> or a user parameter containing command substitution syntax. When the workflow runs, the shell interprets the injected payload and executes attacker-controlled commands on the plugin host. The injected commands inherit the plugin's filesystem access, network reachability, and any mounted credentials.
No verified public proof-of-concept is available. See the Rapid7 Extension Overview for plugin documentation and configuration details.
Detection Methods for CVE-2026-8664
Indicators of Compromise
- Finger Plugin invocations containing shell metacharacters such as ;, |, &, $(, or backticks within the user or host parameters.
- Unexpected child processes spawned by the Finger Plugin runtime, particularly shells, network utilities, or interpreters like bash, sh, curl, wget, python, or nc.
- Outbound network connections from the plugin host to addresses that are not legitimate finger targets.
Detection Strategies
- Inspect InsightConnect workflow logs for Finger Plugin steps containing unusual characters in the user or host input fields.
- Apply process-lineage analytics on the plugin host to flag any non-finger child process descending from the plugin executor.
- Correlate authenticated InsightConnect user sessions with high-risk plugin parameter values to identify abuse by valid accounts.
Monitoring Recommendations
- Enable verbose audit logging on InsightConnect for plugin parameter values and workflow modifications.
- Forward Linux host process and command-line telemetry from plugin runners to a centralized analytics platform.
- Alert on egress traffic from plugin hosts to destinations outside an approved allowlist.
How to Mitigate CVE-2026-8664
Immediate Actions Required
- Update the Rapid7 InsightConnect Finger Plugin to the latest version published on the Rapid7 Extension Library.
- Restrict InsightConnect permissions so only trusted operators can run or edit workflows that invoke the Finger Plugin.
- Audit recent Finger Plugin executions for parameter values containing shell metacharacters.
Patch Information
Consult the Rapid7 Extension Overview for the patched plugin release and release notes. Apply the vendor-supplied update across all InsightConnect orchestrators that have the Finger Plugin enabled.
Workarounds
- Disable or remove the Finger Plugin from InsightConnect environments where it is not actively required.
- Enforce strict input validation at the workflow level by constraining user and host parameters to alphanumeric characters, dots, and hyphens.
- Run the plugin in an isolated container with minimal privileges, no persistent credentials, and restricted outbound network access.
# Configuration example: restrict outbound traffic from the plugin host
# Allow only DNS and finger protocol (TCP/79) egress
iptables -A OUTPUT -p udp --dport 53 -j ACCEPT
iptables -A OUTPUT -p tcp --dport 79 -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
