CVE-2026-82082 — CVSS 9.8 CRITICAL Severity | NVD Vulnerability Record

Executive Summary

NUMail, the email platform from Green‑Computing, contains an unauthenticated OS command injection flaw (CVE‑2026‑82082) that allows remote attackers to execute arbitrary system commands. The vulnerability carries a CVSS 9.8 (Critical) score, indicating immediate risk of full server compromise for any organization running the affected product. Decision makers must authorize emergency mitigation (e.g., WAF rule deployment or service isolation) and initiate vendor coordination within the next 24 hours.

Verified Facts

• NUMail developed by Green‑Computing is vulnerable to OS command injection — NVD record.
• Unauthenticated remote attackers can inject and execute arbitrary OS commands on the server — NVD record.
• The vulnerability is assigned CVSS 3.1 base score 9.8 (Critical) with vector AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H — NVD record.

Threat Classification

Threat type: Remote code execution via OS command injection (HIGH CONFIDENCE). Affected sector: Email service providers and any enterprise deploying NUMail (MEDIUM CONFIDENCE). Geographic scope: Global, as the product is marketed internationally (MEDIUM CONFIDENCE). Exploitation status: Publicly disclosed with no known public exploit, but the low attack complexity makes rapid weaponization likely (MEDIUM CONFIDENCE). Attacker motivation is not stated in the source (UNKNOWN).

Threat Severity Assessment

• Exploitability – remote, unauthenticated, low complexity (HIGH CONFIDENCE).
• Impact – potential full system compromise, data exfiltration, and service outage (HIGH CONFIDENCE).
• Prevalence – product is commercially available and likely deployed in multiple organizations (MEDIUM CONFIDENCE).
• CVSS score of 9.8 confirms Critical severity (HIGH CONFIDENCE).

Business Impact

Successful exploitation grants attackers OS‑level control, enabling deletion or alteration of email data, credential theft, and lateral movement, which can halt business communications and breach confidentiality obligations under GDPR or NIS2. The breach of personal data triggers mandatory regulator notification and potential fines, while service interruption erodes customer trust and can lead to contract penalties.

Technical Analysis

• Attack vector: Network‑based HTTP request to the NUMail web interface (AV:N).
• Exploitation chain: Attacker sends a crafted parameter containing OS command syntax; insufficient input sanitization allows the command to be passed to the underlying shell; the shell executes the command with the privileges of the NUMail service process.
• Affected component: NUMail server‑side request handling module (specific version not disclosed).
• Root cause: Improper validation of user‑supplied input leading to OS command injection (CWE‑78).
• CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

CVE Analysis

• CVE‑2026‑82082 – NUMail (Green‑Computing) – CWE‑78 OS Command Injection – Network attack vector – No authentication required – No patch or mitigation disclosed in the source.

MITRE ATT&CK Mapping

• Initial Access → T1190 Exploit Public‑Facing Application — the vulnerability is a publicly exposed web service that can be directly exploited.
• Execution → T1059.007 Command Shell — injected payload results in execution of OS shell commands.

IOC Intelligence

No public IOCs confirmed at time of publication.

Behavioral IOC categories for rule creation:

• HTTP request URIs or parameters containing command‑separator characters such as “;”, “|”, “&&”, “`”.
• Process creation events where a web‑server process (e.g., httpd, nginx, w3wp.exe) spawns a shell interpreter (cmd.exe, /bin/sh, /bin/bash).
• Outbound network connections initiated by a newly spawned shell process to external IP addresses not previously contacted by the web server.
• File system writes to system directories (e.g., /etc/, C:\Windows\System32) by the web‑server process shortly after a suspicious request.

Detection Engineering Guidance

• Collect web server access logs (e.g., Apache access_log, IIS W3C logs) and query for request lines matching the regex [\;\|\&\&\`] in query parameters.
• Enable Sysmon Event ID 1 (Process Creation) on Windows hosts; alert when ParentImage equals a known web‑server executable and Image equals cmd.exe or powershell.exe with command‑line arguments containing the same injection characters.
• On Linux, enable auditd rule -a always,exit -F arch=b64 -S execve -F exe=/usr/sbin/httpd -k webcmd and monitor for exe=/bin/sh with suspicious arguments.
• Correlate process creation alerts with subsequent outbound connections (Netflow, Zeek) from the same host within a 5‑minute window.
• Deploy a WAF rule that blocks requests containing the pattern (;|\||&&|`) in any parameter.

Sigma Rules

title: Suspicious Shell Execution from Web Server Process
id: 3f9c2a1e-5b4d-4e9a-9c2f-1a2b3c4d5e6f
status: stable
description: Detects cmd.exe or /bin/sh spawned by a known web server process, indicating possible OS command injection.
author: CYBERDUDEBIVASH Sentinel APEX
logsource:
    product: windows
    service: sysmon
detection:
    selection_parent:
        ParentImage|endswith:
            - '\w3wp.exe'
            - '\http

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