CVE-2021-4106

Executive Summary

CVE-2021-4106 is a privilege escalation vulnerability in the Snow Inventory Java Scanner, version 1.0, a component of the Snow Software asset inventory suite. The flaw allows an authenticated local attacker to execute arbitrary code with elevated privileges, potentially compromising the host operating system and any adjacent infrastructure. The vulnerability carries a CVSS score of 7.8 (High), reflecting full confidentiality, integrity, and availability impact, though exploitation requires local access and no user interaction. The vendor recommends upgrading to version 2.0, but this patch is not independently confirmed, and no public exploit or PoC has been observed as of this writing.

Technical Analysis

Insufficient technical detail available from the provided CVE data. The NVD description states only that the vulnerability "allows an attacker to run malicious code at a higher level of privileges" in the Snow Inventory Java Scanner version 1.0. No CWE classification, vulnerable function names, specific code paths, or exploitation mechanics are disclosed in the available data.

The vulnerability class is best characterized as improper privilege management (CWE-269). The Snow Inventory Java Scanner is a Java-based agent that collects hardware and software inventory data on endpoints and forwards it to a central Snow Inventory server. Such agents typically run with elevated privileges (SYSTEM/root) to enumerate installed applications, registry keys, filesystem metadata, and other system-level inventory data. A flaw in how the scanner handles input — whether through command-line arguments, configuration files, or inter-process communication — could allow a lower-privileged user to inject malicious instructions that execute within the scanner's elevated context.

The attack surface is the local execution environment. Any authenticated user on an affected host may be able to trigger the vulnerable code path. Because Java agents commonly load plugins, read external configuration, or invoke external processes during the inventory collection cycle, the vulnerability may be triggered during normal scanner operation or via a crafted payload delivered locally.

The CVSS vector indicates local attack vector (AV:L), low attack complexity (AC:L), and low privilege requirement (PR:L), meaning a standard unprivileged user can exploit the flaw. No user interaction (UI:N) is needed, and the scope is unchanged (S:U). The full CIA triad impact (H:H:H) suggests code execution with the scanner's privilege level, which is typically elevated.

It is important to note that the absent CWE classification and sparse technical description limit the depth of code-level analysis. No function names, class names, file paths, or specific parameter names are provided in the NVD description or CNA title, and none are assumed in this report.

Exploitation Scenarios

The exploitation chain is inferred from the vulnerability class (privilege escalation via malicious code execution) and the available technical details. No public PoC exists; the attack chain below is a best-effort reconstruction.

Step 1 — Reconnaissance / Target Identification: An attacker with a valid account on an endpoint identifies whether the Snow Inventory Java Scanner 1.0 is installed. This can be achieved by checking running Java processes, inspecting installed programs, or enumerating scheduled tasks. The scanner may also be identified by its default installation paths or service names, though specific identifiers are not disclosed in the available data.

Step 2 — Triggering the Flaw: The attacker crafts an input designed to be processed by the Java Scanner during its inventory collection cycle. Because the vulnerable mechanism is unconfirmed, plausible vectors include:

• Supplying a malicious configuration file or command-line argument that the scanner parses with elevated privileges.
• Dropping a payload in a directory the scanner monitors or reads during inventory enumeration.
• If the scanner reads from a named pipe or socket, the attacker may transmit a malicious payload directly.

Since the vulnerability requires low privileges (PR:L) and local access (AV:L), the attacker does not need administrative rights or user interaction to trigger the flaw. The scanner's automation may self-trigger on the malicious input once placed.

Step 3 — Payload / Execution Method: The payload is designed to exploit the privilege boundary and execute arbitrary code at the scanner's privilege level (likely SYSTEM on Windows or root on Unix derivatives). The execution method depends on the underlying flaw — if the scanner deserializes untrusted data, a crafted serialized object could lead to code execution; if it invokes external processes with unsanitized user input, command injection may be achievable; if it loads Java classes from attacker-controlled paths, a malicious JAR could execute.

Step 4 — Post-Exploitation Impact: Successful exploitation yields code execution with elevated privileges. The attacker gains full control of the affected host — reading credentials stored in the registry or configuration files, disabling security controls, pivoting to other systems on the network, or planting persistent backdoors. Because the scanner is a legitimate, signed component, files placed by the attacker may evade application whitelisting and security monitoring.

Impact Assessment

Business Impact: The Snow Inventory Java Scanner is deployed on endpoints across enterprise fleets, including servers and workstations, as part of asset and license management programs. A privilege escalation vulnerability in this component undermines the security of any machine running version 1.0. Full compromise of an endpoint can lead to data exfiltration, lateral movement, and eventually domain-wide compromise if the host holds domain account credentials or access to sensitive systems.

CVSS Breakdown (based on vector 7.8):

• Attack Vector: Local (L) — requires local access; reduces remote exploitability but is commonly reachable via malware or phishing.
• Attack Complexity: Low (L) — no unusual conditions required.
• Privileges Required: Low (L) — a standard unprivileged user account suffices.
• User Interaction: None (N) — no victim interaction needed.
• Scope: Unchanged (U) — the compromise is limited to the affected component's security bounding, but this is the scanner running with high privileges.
• Confidentiality / Integrity / Availability: High (H/H/H) — full read/write/execute control over the host.

Blast Radius: Every endpoint with Snow Inventory Java Scanner 1.0 is at risk. Inventory agents are often installed widely across fleets for compliance and license management, meaning the vulnerable population can be substantial. Organizations in regulated industries relying on Snow Inventory for audit evidence face additional compliance risk if endpoints are compromised.

Exploit Intelligence: EPSS score is 0.00253, placing this CVE in the 16.8th percentile — a low likelihood of exploitation in the wild based on current telemetry. It is not listed in CISA's Known Exploited Vulnerabilities catalog, and no public exploit code or PoC has been identified. The threat actor interest is presently low, but the vulnerability remains attractive to attackers with local access who seek privilege escalation in enterprise environments.

Detection Guidance

Detection of this vulnerability focuses on anomalous behavior of the Java Scanner process: unexpected child processes, reads/writes to unusual locations, or modification of inventory data. The rules below are generic templates designed to detect privilege escalation attempts.

Sigma Rule

title: Suspicious Child Process from Snow Inventory Java Scanner
id: 3c0e6a1b-8f4d-4c7a-9b2e-5d1a2f3c4d5e
status: experimental
description: Detects the Snow Inventory Java Scanner spawning unusual child processes, potentially indicating CVE-2021-4106 exploitation
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2021-4106
author: Valters IT Security Team
date: 2025/01/15
logsource:
  category: process_creation
  product: windows
detection:
  selection_parent:
    ParentImage|endswith:
      - '\snowinventory.jar'
      - '\snowinventory.exe'
      - '\javaw.exe'
  selection_child:
    Image|endswith:
      - '\cmd.exe'
      - '\powershell.exe'
      - '\wscript.exe'
      - '\cscript.exe'
      - '\rundll32.exe'
  filter_known:
    ParentCommandLine|contains:
      - 'normal'
      - 'inventory'
  condition: selection_parent and selection_child and not filter_known
level: high
falsepositives:
  - Legitimate scanner sub-processes (review command-line arguments)
tags:
  - attack.privilege_escalation
  - attack.t1068

YARA Rule

rule CVE_2021_4106_SnowInventoryScanner_Suspicious {
    meta:
        author = "Valters IT Security Team"
        description = "Detects suspicious files or payloads related to Snow Inventory Java Scanner 1.0 privilege escalation"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2021-4106"
        date = "2025-01-15"
        score = 60

    strings:
        $snow_ref = "snow" ascii wide nocase
        $snow_scanner = "inventory" ascii wide nocase
        $java_token = "java" ascii wide nocase
        $elevation = "privilege" ascii wide nocase
        $shell = "cmd.exe" ascii wide nocase
        $ps = "powershell" ascii wide nocase

    condition:
        uint16(0) == 0x5A4D and                    // PE file
        (($snow_scanner or $snow_ref) and $java_token) and
        (1 of ($shell, $ps) or $elevation)
}

Note: This YARA rule is a generic template for files referencing the vulnerable product and common payload indicators. Specific detection requires knowledge of the vuln's mechanics, which are not disclosed.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2021-4106 - Snow Inventory Java Scanner Suspicious Download"; flow:established,to_client; content:"snow"; nocase; content:"inventory"; nocase; distance:0; content:"jar"; distance:0; fileext:"jar"; classtype:attempted-user; sid:2061001; rev:1; reference:url,https://nvd.nist.gov/vuln/detail/CVE-2021-4106;)

Note: Network-based detection is of limited value for this local privilege escalation vulnerability. The above rule flags download of scanner-related JAR files over HTTP. Local host monitoring is more effective.

Elastic Detection

// Detect Snow Inventory Scanner spawning suspicious child processes
process where event.type == "start" and
  process.parent.name in ("javaw.exe", "java.exe", "snowinventory.exe") and
  process.parent.command_line contains "snow" and
  process.name in ("cmd.exe", "powershell.exe", "wscript.exe", "rundll32.exe") and
  not process.command_line contains "inventory"

Splunk SPL Query

index=windows sourcetype=WinEventLog:Security EventCode=4688
| where Parent_Process_Name LIKE "%snow%" OR Parent_Process_Name LIKE "%java%"
| where Parent_Command_Line LIKE "%inventory%"
| where New_Process_Name LIKE "%cmd.exe%" OR New_Process_Name LIKE "%powershell.exe%" 
  OR New_Process_Name LIKE "%wscript.exe%" OR New_Process_Name LIKE "%rundll32.exe%"
| table TimeCreated, User_Name, Parent_Process_Name, Parent_Command_Line, New_Process_Name, New_Process_Command_Line
| sort -TimeCreated

Wazuh OSSEC Rule

<group name="snow_inventory,">
  <rule id="176001" level="12">
    <if_sid>550</if_sid>
    <match>powershell.exe|cmd.exe|wscript.exe</match>
    <regex>javaw.exe.*snow|java.exe.*inventory</regex>
    <description>Snow Inventory Java Scanner spawning suspicious child process - potential CVE-2021-4106 exploitation</description>
    <group>privilege_escalation,</group>
    <mitre>
      <id>T1068</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED — The CNA (Snow Software) states that version 2.0 resolves the vulnerability, but this has not been independently confirmed by a second source. Until confirmation, treat the fix as provisional and apply additional mitigations.

Immediate Mitigations:

1. Restrict local access: Remove unprivileged users from endpoints running Snow Inventory Java Scanner 1.0 where feasible. Since the flaw requires local access with low privileges, reducing the local user population reduces exposure.
2. Least privilege for the scanner: If configuration permits, run the scanner with reduced privileges rather than SYSTEM/root. This limits the impact of successful exploitation.
3. Monitor the scanner process: Deploy the detection rules above (Sigma/EQL/SPL) to alert on anomalous behavior of the Java scanner process. Investigate all alerts promptly.
4. Application whitelisting: Restrict which executables the scanner process can spawn, using tools like Windows Defender Application Control or AppLocker.
5. Network segmentation: Isolate endpoints running the vulnerable scanner, particularly high-value servers, to limit lateral movement post-exploitation.

Patch/Upgrade Steps:

1. Contact Snow Software support to confirm the availability of version 2.0.
2. Validate the fix in a test environment, including regression testing of inventory collection.
3. Plan a phased rollout across the fleet, prioritizing internet-facing or high-risk endpoints.
4. After deployment, verify version 2.0 is active and inventory data is being collected correctly.

Long-Term Hardening:

1. Establish a vendor patch review process to validate single-source patches with independent verification before enterprise-wide deployment.
2. Minimize the footprint of privileged agents — audit all software running with SYSTEM/root privileges on endpoints.
3. Implement a rigorous least-privilege model for local accounts; consider LAPS (Local Administrator Password Solution) or equivalent.
4. Enable comprehensive logging (Process Creation, PowerShell, etc.) and integrate with SIEM for continuous monitoring.
5. Maintain an asset inventory of all Snow Inventory Scanner installations to facilitate rapid patching in future incidents.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2021-4106
2. CVE.org Record: https://www.cve.org/CVERecord?id=CVE-2021-4106
3. Snow Software - Vendor: https://www.snowsoftware.com (product advisory page — specific advisory URL not provided in available data)
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2021-4106 NOT listed as of January 2025)
5. FIRST EPSS Explorer: https://www.first.org/epss/search?cve=CVE-2021-4106 (EPSS score 0.00253)

Threat Actor Activity / Exploit-in-the-Wild Evidence: No known threat actor campaigns, exploit code, or in-the-wild exploitation have been reported for CVE-2021-4106 as of this writing. The CVE is not listed in CISA's KEV catalog, and no public PoC has been identified. The low EPSS score (16.8th percentile) corroborates the absence of observed exploitation activity.