What is the CVSS score of CVE-2021-21556?

CVE-2021-21556 has a CVSS 3.1 base score of 6.7 (Medium). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.3%.

Poweredge R740 Firmware CVE-2021-21556

MEDIUM

Stack-based Buffer Overflow (CWE-121)

2021-06-14 security_alert@emc.com

RCE Buffer Overflow Denial Of Service Information Disclosure Stack Overflow Dell Poweredge R740 Firmware Poweredge R740Xd Firmware Poweredge R640 Firmware Poweredge R940 Firmware Poweredge R840 Firmware Poweredge R940Xa Firmware Poweredge T640 Firmware Poweredge Mx740C Firmware Poweredge Mx840C Firmware

6.7

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-121 ASVS 5.0 V15 - Secure Coding and Architecture Stack buffer bounds checking MITRE ATT&CK 1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS score of 6.7 (MEDIUM). Attack characteristics: local attack vector, low complexity, high privileges required, no user interaction not required.
Exploit ScenarioDerived	Successful exploitation could compromise the medium-severity affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

No patch listed yet 0.3% exploitation probability (EPSS)

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AnalysisAI

Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a stack-based buffer overflow vulnerability in systems with NVDIMM-N installed. Rated medium severity (CVSS 6.7), this vulnerability is low attack complexity. No vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-121. Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a stack-based buffer overflow vulnerability in systems with NVDIMM-N installed. A local malicious user with high privileges may potentially exploit this vulnerability, leading to a denial of Service, arbitrary code execution, or information disclosure in UEFI or BIOS Preboot Environment. Affected products include: Dell Poweredge R640 Firmware, Dell Poweredge R740 Firmware, Dell Poweredge R740Xd Firmware, Dell Poweredge R940 Firmware, Dell Poweredge R840 Firmware.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 6.7 MEDIUM

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

Low

Privileges Required

High

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

Dell PowerEdge R640, R740, R740XD, R840, R940, R940xa, MX740c, MX840c, and T640 Server BIOS contain a stack-based buffer overflow vulnerability in systems with NVDIMM-N installed. A local malicious user with high privileges may potentially exploit this vulnerability, leading to a denial of Service, arbitrary code execution, or information disclosure in UEFI or BIOS Preboot Environment.

Threat Intelligence Overview

EPSS Score

0.3%

Top 78% exploitable

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC No

EPSS 0.3%

Patch available No

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Defer

Exploitation· derived

None

System Exposure· derived

Small

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +34

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Stack-based Buffer Overflow HIGH

A stack-based buffer overflow occurs when a program writes more data to a buffer located on the stack than it was allocated to hold.

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)NVD

cpe:2.3:o:dell:poweredge_r640_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_r740_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_r740xd_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_r940_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_r840_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_r940xa_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_t640_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_mx740c_firmware:*:*:*:*:*:*:*:*

cpe:2.3:o:dell:poweredge_mx840c_firmware:*:*:*:*:*:*:*:*

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Same weakness CWE-121 – Stack-based Buffer Overflow

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References

Advisories & patches

ADVISORY https://www.dell.com/support/kbdoc/000187958

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GitHub PoC

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