CVE-2021-20740 – This vulnerability allows remote authenticated ... (How to Fix)

Q: What is the severity of CVE-2021-20740?

CVE-2021-20740 has a CVSS score of 8.8 (HIGH). This vulnerability allows remote authenticated attackers to execute arbitrary operating system commands with root privileges on affected Hitachi and NEC storage systems. Attackers can gain complete control over the system through unspecified vectors. Organizations using vulnerable versions of Hitachi Virtual File Platform or NEC Storage M Series NAS Gateway are affected.

📋 TL;DR

This vulnerability allows remote authenticated attackers to execute arbitrary operating system commands with root privileges on affected Hitachi and NEC storage systems. Attackers can gain complete control over the system through unspecified vectors. Organizations using vulnerable versions of Hitachi Virtual File Platform or NEC Storage M Series NAS Gateway are affected.

💻 Affected Systems

Products:

Hitachi Virtual File Platform
NEC Storage M Series NAS Gateway Nh4a/Nh8a
NEC Storage M Series NAS Gateway Nh4b/Nh8b
NEC Storage M Series NAS Gateway Nh4c/Nh8c

Versions: Hitachi: prior to 5.5.3-09 and prior to 6.4.3-09; NEC: Nh4a/Nh8a prior to FOS 5.5.3-08(NEC2.5.4a), Nh4b/Nh8b/Nh4c/Nh8c prior to FOS 6.4.3-08(NEC3.4.2)

Operating Systems: Proprietary storage OS

Default Config Vulnerable: ⚠️ Yes

Notes: Requires authenticated access; unspecified vectors mean multiple potential attack paths exist.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise with root-level access, allowing data theft, destruction, ransomware deployment, and lateral movement to other systems.

🟠

Likely Case

Privilege escalation leading to data exfiltration, system manipulation, or persistence establishment by authenticated attackers.

🟢

If Mitigated

Limited impact if strong authentication controls, network segmentation, and least privilege principles are enforced.

🌐 Internet-Facing: HIGH - If systems are exposed to the internet, authenticated attackers can achieve full compromise.

🏢 Internal Only: HIGH - Even internally, authenticated users can escalate to root privileges and compromise systems.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: LOW - Once authenticated, exploitation appears straightforward based on CVSS and description.

No public exploit code identified, but authenticated access requirement lowers barrier for internal threats.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Hitachi: 5.5.3-09 or 6.4.3-09; NEC: Nh4a/Nh8a: FOS 5.5.3-08(NEC2.5.4a), Nh4b/Nh8b/Nh4c/Nh8c: FOS 6.4.3-08(NEC3.4.2)

Vendor Advisory: https://www.hitachi.co.jp/products/it/storage-solutions/global/sec_info/2021/2021_306.html

Restart Required: Yes

Instructions:

1. Identify affected systems and versions. 2. Download appropriate patches from vendor portals. 3. Apply patches following vendor documentation. 4. Restart systems as required. 5. Verify patch application.

🔧 Temporary Workarounds

Network Segmentation

all

Restrict network access to storage systems to only necessary administrative networks.

Authentication Hardening

all

Implement strong authentication controls, multi-factor authentication, and strict access policies.

🧯 If You Can't Patch

Isolate affected systems in dedicated network segments with strict firewall rules
Implement strict monitoring and alerting for unusual authentication or command execution patterns

🔍 How to Verify

Check if Vulnerable:

Check system version via administrative interface or CLI; compare against affected versions list.

Check Version:

Vendor-specific CLI commands vary; consult Hitachi or NEC documentation for version checking.

Verify Fix Applied:

Verify system version matches patched versions after update and restart.

📡 Detection & Monitoring

Log Indicators:

Unusual authentication patterns
Unexpected command execution events
Privilege escalation attempts

Network Indicators:

Unexpected administrative connections to storage systems
Anomalous outbound traffic from storage systems

SIEM Query:

source="storage_system" AND (event_type="command_execution" OR auth_user="*" AND action="privilege_change")

📊 Metadata

CVE ID: CVE-2021-20740

CVSS v3 Score: 8.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-78

Published: June 28, 2021

Last Updated: November 21, 2024

🔗 References

https://jpn.nec.com/security-info/secinfo/nv21-011.html Vendor Advisory
https://jvn.jp/en/jp/JVN21298724/index.html Third Party Advisory
https://www.hitachi.co.jp/products/it/storage-solutions/global/sec_info/2021/2021_306.html Vendor Advisory
https://jpn.nec.com/security-info/secinfo/nv21-011.html Vendor Advisory
https://jvn.jp/en/jp/JVN21298724/index.html Third Party Advisory
https://www.hitachi.co.jp/products/it/storage-solutions/global/sec_info/2021/2021_306.html Vendor Advisory

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