CVE-2021-38687
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA stack buffer overflow vulnerability in QNAP Surveillance Station allows remote attackers to execute arbitrary code due to improper bounds checking. This critical flaw in the surveillance software component can be exploited over the network without authentication, potentially giving attackers full control of the affected NAS device.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 5.2.0.4.2< 5.2.0.3.2< 5.1.5.4.6< 5.1.5.3.6CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm Surveillance Station is installedLog into QNAP NAS and navigate to App Center or check if Surveillance Station appears in the application listAffected if Surveillance Station is installed and running on the NAS device
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Identify the QTS firmware versionIn the QNAP admin interface, go to Control Panel > System > Firmware Update or check the System Dashboard for the QTS version numberAffected if Running QTS 5.0.0 64-bit, QTS 5.0.0 32-bit, QTS 4.3.6 64-bit, or QTS 4.3.6 32-bit/QTS 4.3.3 (these are the firmware versions with corresponding affected Surveillance Station versions)
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Find the installed Surveillance Station versionOpen Surveillance Station, go to Settings > General > Version Info to display the exact version numberAffected if The displayed version falls below the threshold for your QTS firmware type (see affected_if for each version range)
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Compare against affected version thresholdsIf on QTS 5.0.0 64-bit: check if version < 5.2.0.4.2; If on QTS 5.0.0 32-bit: check if version < 5.2.0.3.2; If on QTS 4.3.6 64-bit: check if version < 5.1.5.4.6; If on QTS 4.3.6 32-bit/QTS 4.3.3: check if version < 5.1.5.3.6Affected if Installed Surveillance Station version is below the threshold that matches your QTS firmware type, meaning the stack buffer overflow vulnerability is present
The NAS is affected if Surveillance Station is installed and its version number is lower than the threshold corresponding to the QTS firmware version in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.1.5.3.65.1.5.4.65.2.0.3.2
Organizations running affected QNAP NAS devices should immediately update Surveillance Station to the specified versions (5.2.0.4.2 or later for QTS 5.0.0 64-bit, 5.2.0.3.2 or later for QTS 5.0.0 32-bit, 5.1.5.4.6 or later for QTS 4.3.6 64-bit, 5.1.5.3.6 or later for QTS 4.3.6 32-bit/QTS 4.3.3) released 2021/10/26 or later.
Surveillance Station 5.2.0.4.2 (QTS 5.0.0 64-bit), 5.2.0.3.2 (QTS 5.0.0 32-bit), 5.1.5.4.6 (QTS 4.3.6 64-bit), or 5.1.5.3.6 (QTS 4.3.6 32-bit and QTS 4.3.3)
- 1. Identify the QTS version running on the QNAP NAS (QTS 5.0.0 64-bit, QTS 5.0.0 32-bit, QTS 4.3.6 64-bit, QTS 4.3.6 32-bit, or QTS 4.3.3)
- 2. Check the current Surveillance Station version installed on the device
- 3. Based on the QTS version, upgrade Surveillance Station to the corresponding fixed version: For QTS 5.0.0 64-bit upgrade to 5.2.0.4.2 or later; For QTS 5.0.0 32-bit upgrade to 5.2.0.3.2 or later; For QTS 4.3.6 64-bit upgrade to 5.1.5.4.6 or later; For QTS 4.3.6 32-bit upgrade to 5.1.5.3.6 or later; For QTS 4.3.3 upgrade to 5.1.5.3.6 or later
- 4. Perform the upgrade through the QNAP App Center or manually download the update from the QNAP download center
- 5. After upgrading, verify the Surveillance Station version matches or exceeds the fixed version for your QTS variant
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-38687 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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