CVE-2021-38687

CRITICAL

A stack buffer overflow vulnerability has been reported to affect QNAP NAS running Surveillance Station. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already...

Affects 2 products across 1 vendor.

BCS7.37
CVSS 3.19.8
EPSS1.3%
Percentile68th
PatchPatched
CVSS Vector — Plain English Remotely exploitable over the network, low complexity, no authentication required, no user interaction needed, impact contained to the vulnerable component, full confidentiality impact, full integrity impact, full availability impact.
CWE Weakness Definitions
CWE-120: Buffer Copy without Checking Size (Classic Buffer Overflow)

Program copies data to a buffer without verifying the source data fits within the destination.

Related Attack Patterns (CAPEC)
CAPEC-8 Buffer Overflow in an API Call
via CWE-120
CAPEC-9 Buffer Overflow in Local Command-Line Utilities
via CWE-120
CAPEC-10 Buffer Overflow via Environment Variables
via CWE-120
CAPEC-14 Client-side Injection-induced Buffer Overflow
via CWE-120
CAPEC-24 Filter Failure through Buffer Overflow
via CWE-120
Show all 13

Mapping is CWE-to-CAPEC per MITRE CAPEC 3.9.

◆ SAGE Intelligence — CITED Relevance Research Team

A stack buffer overflow vulnerability in QNAP NAS running Surveillance Station allows attackers to execute arbitrary code.

BSID: BS-2021-GLOBAL-071727-C • Model: /workspace/models/qwen2.5-coder-32b-instruct-bf16 • Confidence: HIGH

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Frequently Asked Questions
What is CVE-2021-38687?
A stack buffer overflow vulnerability in QNAP NAS running Surveillance Station allows attackers to execute arbitrary code.
What is the CVSS score for CVE-2021-38687?
CVE-2021-38687 has CVSS 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS: 1.3%.
Is CVE-2021-38687 actively exploited?
No confirmed active exploitation of CVE-2021-38687 as of 2026-05-30.
How do I remediate CVE-2021-38687?
Priority: IMMEDIATE. Advisory: https://www.qnap.com/en/security-advisory/qsa-21-46 PSIRT: [email protected]
What systems are affected by CVE-2021-38687?
CVE-2021-38687 affects: Qnap, Qnap.
Vulnerability Details
CVE IDCVE-2021-38687
BSIDBS-2021-GLOBAL-071727-C BreachSpider Global ID
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published2021-12-29
Last Modified2024-11-21
ICS Relevance80%
Weakness (CWE)
SourceNVD
Official Description

A stack buffer overflow vulnerability has been reported to affect QNAP NAS running Surveillance Station. If exploited, this vulnerability allows attackers to execute arbitrary code. We have already fixed this vulnerability in the following versions of Surveillance Station: QTS 5.0.0 (64 bit): Surveillance Station 5.2.0.4.2 ( 2021/10/26 ) and later QTS 5.0.0 (32 bit): Surveillance Station 5.2.0.3.2 ( 2021/10/26 ) and later QTS 4.3.6 (64 bit): Surveillance Station 5.1.5.4.6 ( 2021/10/26 ) and later QTS 4.3.6 (32 bit): Surveillance Station 5.1.5.3.6 ( 2021/10/26 ) and later QTS 4.3.3: Surveillance Station 5.1.5.3.6 ( 2021/10/26 ) and later

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

The vulnerability is exploited through a buffer overflow in the handling of certain network packets, leading to arbitrary code execution.

Exploitation Likelihood: HIGH

Affected Products
VendorProductFixed Version
Qnap Qts
Qnap Surveillance Station
Remediation
View Vendor Advisory →

Remediation Priority: IMMEDIATE

Vendor PSIRT: [email protected]
Threat Intelligence
● Threat Intelligence Validated: August 2026 | Threat Age: 1691 Days
CISA KEVNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
SAGE Enrichment Record — provenance & audit hash
Model/workspace/models/qwen2.5-coder-32b-instruct-bf16
ConfidenceHIGH
Enriched At2026-05-24
SHA-512 Audit Hash60a50b26417cc7d904f0064603512cb03514a0ee3165b6ea55a1d5a5d9e1624451b6e88327e9da1130e7653ac3f813ffe928c2905f671e0937cbbaf255103d78
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