CVE-2026-9155: Rapid7 InsightConnect Sed Plugin OS Command Injection (CVSS 8.8)

Technical summary

CVE-2026-9155 is an OS command injection vulnerability (CWE-78) in the Rapid7 InsightConnect Sed Plugin running on Linux. The plugin fails to properly sanitize the expression parameter before passing it to the underlying sed command interpreter. Attackers who possess valid InsightConnect credentials can craft malicious expressions containing shell metacharacters or command substitution syntax to break out of the intended sed context and execute arbitrary commands with the service's effective user privileges. The CVSS 3.1 score of 8.8 (HIGH) reflects the high impact potential: confidentiality, integrity, and availability are all compromised, though exploitation requires prior authentication.

Business impact

In environments where InsightConnect orchestrates security or IT operations workflows, a compromised authenticated account or insider threat can pivot through the Sed Plugin to achieve remote code execution on connected Linux systems. This threatens the integrity of automated incident response, the confidentiality of data processed by workflows, and availability of critical services managed through InsightConnect. Organizations relying on this plugin for sensitive automation should treat this as a privilege escalation and lateral movement vector.

Affected systems

The vulnerability directly affects the Rapid7 InsightConnect Sed Plugin on Linux systems. The underlying sed tool (gnu sed) and Linux kernel are listed in the affected product taxonomy, but the actual vulnerability is in how InsightConnect invokes sed without proper input validation. Any Linux deployment running InsightConnect with the Sed Plugin enabled is at risk if authenticated access to the platform is possible or if an authenticated user's credentials are compromised.

Exploitability

Exploitation requires valid InsightConnect authentication credentials (PR:L in the CVSS vector). Once authenticated, an attacker can immediately craft and execute a malicious expression without user interaction—the attack is straightforward, with no complex timing or race conditions. Network accessibility is required (AV:N), but authentication is the primary gate. This is not currently tracked in the CISA KEV catalog, indicating it may not yet have proof-of-concept code in the wild or active exploitation reports, but the low complexity and high impact suggest it warrants proactive patching.

Remediation

Contact Rapid7 for a patched version of the InsightConnect Sed Plugin. Patch releases should include input validation and sanitization of the expression parameter, preventing shell metacharacter injection. Until patched, restrict InsightConnect authentication to trusted operators, implement principle of least privilege for the service account running InsightConnect, and monitor for suspicious expression parameters in audit logs. Isolate or remove the Sed Plugin if it is not actively used in your workflows.

Patch guidance

Verify the latest security advisory from Rapid7 InsightConnect for plugin patch versions addressing CVE-2026-9155. Update the Sed Plugin to the patched version as soon as testing confirms compatibility with your InsightConnect deployment. Apply the patch to all Linux systems running the vulnerable plugin. After patching, validate that existing workflows still execute correctly and review expression parameters in automation rules for any that might have inadvertently relied on shell command injection.

Detection guidance

Monitor InsightConnect audit and plugin logs for expression parameters containing shell metacharacters (backticks, $(), |, ;, &&, ||, >, <, etc.). Alert on any expression submitted to the Sed Plugin that deviates from expected sed syntax. Network-based detection is limited since the plugin executes locally; instead, focus on endpoint logging via auditd or similar tools to detect child processes spawned from the InsightConnect service account with unexpected command lines. Behavioral analysis of the InsightConnect process and its children can reveal command injection attempts.

Why prioritize this

This vulnerability scores HIGH (8.8 CVSS) with full impact on confidentiality, integrity, and availability. Although it requires authentication, it represents a significant insider threat and credential compromise risk in automation-heavy security operations centers. The combination of remote network access, low attack complexity, and high impact makes it suitable for urgent patching, especially in organizations where InsightConnect credentials are shared or where there is elevated insider risk.

Risk score, explained

The CVSS 3.1 score of 8.8 reflects: Network-accessible endpoint (AV:N), low attack complexity due to straightforward command injection (AC:L), requirement for low-privilege authentication (PR:L), no user interaction needed (UI:N), and high impact across all three security properties (C:H, I:H, A:H). The authentication requirement prevents a critical rating, but the ease of exploitation once authenticated and the severity of impact justify the HIGH classification.

Frequently asked questions