What is the CVSS score of CVE-2021-28797?

CVE-2021-28797 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 5.9%.

Surveillance Station CVE-2021-28797

CRITICAL

Stack-based Buffer Overflow (CWE-121)

2021-04-14 security@qnapsecurity.com.tw

RCE Buffer Overflow Qnap Stack Overflow Surveillance Station

9.8

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 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

No patch listed yet 5.9% exploitation probability (EPSS)

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AnalysisAI

A stack-based buffer overflow vulnerability has been reported to affect QNAP NAS devices running Surveillance Station. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, 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

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Technical ContextAI · show details

This vulnerability is classified under CWE-121. A stack-based buffer overflow vulnerability has been reported to affect QNAP NAS devices running Surveillance Station. If exploited, this vulnerability allows attackers to execute arbitrary code. QNAP have already fixed this vulnerability in the following versions: Surveillance Station 5.1.5.4.3 (and later) for ARM CPU NAS (64bit OS) and x86 CPU NAS (64bit OS) Surveillance Station 5.1.5.3.3 (and later) for ARM CPU NAS (32bit OS) and x86 CPU NAS (32bit OS) Affected products include: Qnap Surveillance Station.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

A stack-based buffer overflow vulnerability has been reported to affect QNAP NAS devices running Surveillance Station. If exploited, this vulnerability allows attackers to execute arbitrary code. QNAP have already fixed this vulnerability in the following versions: Surveillance Station 5.1.5.4.3 (and later) for ARM CPU NAS (64bit OS) and x86 CPU NAS (64bit OS) Surveillance Station 5.1.5.3.3 (and later) for ARM CPU NAS (32bit OS) and x86 CPU NAS (32bit OS)

Threat Intelligence Overview

EPSS Score

5.9%

Top 8% 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 CRITICAL

CISA KEV No

Public POC No

EPSS 5.9%

Patch available No

Active threat No

Deciding rule

CRITICAL severity

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

Scheduled

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +6

CVSS: +49

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.

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.