CVE-2026-9153

Executive Summary

CVE-2026-9153 is an Arbitrary File Read vulnerability in the Rapid7 InsightConnect Sed Plugin on Linux. The flaw allows authenticated attackers to read arbitrary files on the host system by manipulating the expression parameter due to insufficient input validation. With a CVSS score of 6.5 (Medium), this vulnerability poses a significant confidentiality risk, as it can lead to the exposure of sensitive data such as configuration files, credentials, and proprietary information. No public proof-of-concept (PoC) or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation activity in the wild. However, the potential impact on organizations using Rapid7 InsightConnect for automation and orchestration is high, especially in environments where the plugin runs with elevated privileges.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a plugin within the Rapid7 InsightConnect ecosystem, which is a commercial SOAR (Security Orchestration, Automation, and Response) platform. The risk is primarily to the host system where the plugin is deployed, not to the software supply chain.

CVSS Breakdown & Threat Level

• CVSS Score: 6.5 (Medium)
• Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
• Attack Vector (AV): Local (L) – The attacker must have local access to the system.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): High (H) – The attacker must be authenticated with high privileges.
• User Interaction (UI): None (N) – No user action is needed.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): High (H) – Complete loss of confidentiality.
• Integrity (I): None (N) – No impact on integrity.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. The requirement for high privileges reduces the attack surface, but the potential for reading sensitive files (e.g., /etc/shadow, SSH keys) makes it a serious concern for internal threats or privilege escalation scenarios.

Deep Dive & Mechanics

The vulnerability resides in the Sed Plugin of Rapid7 InsightConnect, which is used to execute sed commands on Linux systems for text processing. The plugin accepts an expression parameter that is passed directly to the sed command without proper sanitization. An authenticated attacker with high privileges can craft a malicious expression that includes file read operations, such as using the r command in sed to read arbitrary files.

Root Cause: Insufficient input validation on the expression parameter. The plugin does not restrict or sanitize the sed commands that can be executed, allowing an attacker to inject file read operations.

Attack Flow:

1. The attacker authenticates to the InsightConnect platform with high privileges.
2. The attacker creates or modifies a workflow that uses the Sed Plugin.
3. The attacker sets the expression parameter to something like 'r /etc/passwd' or 'w /tmp/output.txt' to read or write files.
4. The plugin executes the sed command with the malicious expression, reading the target file and potentially outputting its contents to the attacker or writing it to a location accessible to the attacker.

Impact: An attacker can read any file on the system that the plugin process has access to, including sensitive configuration files, credentials, and application data.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the current implementation of the Sed Plugin. A patched version would need to implement strict input validation and sanitization.

Vulnerable Code (Conceptual):

import subprocess

def run_sed(expression, file_path):
    command = f"sed '{expression}' {file_path}"
    result = subprocess.run(command, shell=True, capture_output=True, text=True)
    return result.stdout

Patched Code (Conceptual):

import subprocess
import re

def run_sed(expression, file_path):
    # Whitelist allowed sed commands
    allowed_commands = ['s', 'd', 'p', 'q', 'a', 'i', 'c', 'y', 'n']
    # Extract the command from the expression
    command_match = re.match(r'^([a-zA-Z])', expression)
    if command_match and command_match.group(1) in allowed_commands:
        command = f"sed '{expression}' {file_path}"
        result = subprocess.run(command, shell=True, capture_output=True, text=True)
        return result.stdout
    else:
        raise ValueError("Invalid sed command")

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a Linux system with Rapid7 InsightConnect Sed Plugin installed.
• High-privileged credentials for the InsightConnect platform.

Exploitation Steps:

1. Log in to the InsightConnect platform.
2. Navigate to the workflow editor and create a new workflow.
3. Add a step using the Sed Plugin.
4. Set the expression parameter to read a sensitive file, e.g., 'r /etc/shadow'.
5. Set the file_path parameter to a dummy file (e.g., /tmp/dummy.txt).
6. Execute the workflow.
7. The output will contain the contents of /etc/shadow.

Example Payload:

# Expression to read /etc/passwd
r /etc/passwd

Alternative Payload (Write to file):

# Expression to write /etc/shadow to /tmp/out.txt
w /tmp/out.txt

Blue Team

Detection:

• Monitor for unusual sed commands executed by the InsightConnect process.
• Look for sed commands with r or w flags that reference sensitive files (e.g., /etc/shadow, /etc/passwd, /root/.ssh/id_rsa).
• Audit InsightConnect logs for workflows using the Sed Plugin with suspicious expressions.

Hunting:

• Search for sed commands in process execution logs that include file read/write operations.
• Correlate with authentication logs to identify high-privileged users triggering these commands.

Lab Setup:

• Install Rapid7 InsightConnect on a Linux VM.
• Configure the Sed Plugin in a workflow.
• Use a test user with high privileges to simulate the attack.
• Monitor system logs and process execution.

Indicators of Compromise (IOCs)

• Process Execution: sed commands with r or w flags targeting sensitive files.
• File Access: Unauthorized reads of /etc/shadow, /etc/passwd, /root/.ssh/, /var/log/, etc.
• Network Traffic: Outbound connections from the InsightConnect server to attacker-controlled systems (if data is exfiltrated).
• Log Entries: InsightConnect audit logs showing Sed Plugin usage with unusual expressions.

Example IOC (Syslog):

Jan 15 10:00:00 server sed[12345]: sed -e 'r /etc/shadow' /tmp/dummy.txt

Detection Engineering

YARA Rule

rule CVE_2026_9153_Sed_Plugin_Exploit {
    meta:
        description = "Detects malicious sed commands exploiting CVE-2026-9153"
        author = "Valters IT"
        date = "2025-01-15"
        reference = "CVE-2026-9153"
    strings:
        $sed_r = /sed\s+.*['\"]r\s+\/[a-zA-Z0-9_\/]+['\"]/
        $sed_w = /sed\s+.*['\"]w\s+\/[a-zA-Z0-9_\/]+['\"]/
    condition:
        any of them
}

Sigma Rule

title: CVE-2026-9153 Sed Plugin Arbitrary File Read
id: 8a4b3c2d-1e5f-4a7b-9c8d-0e1f2a3b4c5d
status: experimental
description: Detects sed commands with file read/write operations targeting sensitive files
author: Valters IT
date: 2025-01-15
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/bin/sed'
        CommandLine|contains:
            - 'r /etc/'
            - 'w /etc/'
            - 'r /root/'
            - 'w /root/'
    condition: selection
falsepositives:
    - Legitimate administrative use of sed for file operations
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-9153 Sed Plugin Data Exfiltration"; flow:to_server,established; content:"sed"; nocase; content:"r /"; distance:0; within:100; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Sed Plugin if not essential for operations.
2. Restrict access to the InsightConnect platform to only trusted users.
3. Monitor logs for suspicious Sed Plugin usage.

Long-term Fix:

• Apply a patch from Rapid7 when available.
• Implement input validation and sanitization for the expression parameter.
• Use a whitelist of allowed sed commands.

Workarounds:

• Replace the Sed Plugin with a custom script that validates inputs.
• Use containerization to isolate the plugin process and limit file system access.

Detection:

• Deploy the provided YARA, Sigma, and Suricata rules.
• Enable auditing of process execution on the InsightConnect server.

Valters IT