Evidence used
- CISA confirms exploitation in the wild.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 33.99% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2020-2509High confidence
QNAP Network-Attached Storage (NAS) Command Injection Vulnerability
QNAP · QNAP Network-Attached Storage (NAS)
9.8CriticalCVSS 3.1
Patch now
Patch availableCISA confirms exploitation in the wild and lists 2022-05-02 as the remediation due date.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityCritical→Operational priority:Critical, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Increase monitoring for the attack path and post-exploitation behaviour described in the report.
Verification
- Confirm that the asset runs QNAP QNAP Network-Attached Storage (NAS) and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
CISA confirms exploitation in the wild and lists 2022-05-02 as the remediation due date.
Patch available01
What, why and how
QNAP NAS devices contain a command injection vulnerability which could allow attackers to perform remote code execution.
What
QNAP NAS devices contain a command injection vulnerability which could allow attackers to perform remote code execution.
Why
Untrusted input reaches a command interpreter without sufficient validation or separation from command syntax.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
What
QNAP NAS devices contain a command injection vulnerability which could allow attackers to perform remote code execution.
Why
Untrusted input reaches a command interpreter without sufficient validation or separation from command syntax.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation Confirmed in the wild
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2022-04-11.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Improper Neutralization of Special Elements used in a Command ('Command Injection') → execute code or commands in the affected security context
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-77 ↗
CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection'). The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Patch available
- Affected
- Fixed
- QNAP has already fixed this vulnerability in the following versions:
- QTS 4.5.2.1566 Build 20210202 and later
- QTS 4.5.1.1495 Build 20201123 and later
- QTS 4.3.6.1620 Build 20210322 and later
- QTS 4.3.4.1632 Build 20210324 and later
- QTS 4.3.3.1624 Build 20210416 and later
- QTS 4.2.6 Build 20210327 and later
- QuTS hero h4.5.1.1491 build 20201119 and later
- Action
- Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 17 Apr 2021 · Last source change 21 Oct 2025, 23:25 UTC · CWE-77 · Improper Neutralization of Special Elements used in a Command ('Command Injection')
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2020-22302
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: qnap.com/qsa-21-05.qnap.com ↗
- Before
- vendor advisory: qnap.com/qsa-21-05
- After
- remediation: qnap.com/qsa-21-05 · vendor advisory: qnap.com/qsa-21-05
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- Before
- unspecified < 4.5.2.1566 Build 20210202; unspecified < 4.5.1.1495 Build 20201123; unspecified < 4.3.6.1620 Build 20210322; unspecified < 4.3.4.1632 Build 20210324; unspecified < 4.3.3.1624 Build 20210416; unspecified < 4.2.6 Build 20210327; unspecified < h4.5.1.1491 build 20201119 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- QTS: unspecified < 4.5.2.1566 Build 20210202, unspecified < 4.5.1.1495 Build 20201123, unspecified < 4.3.6.1620 Build 20210322, unspecified < 4.3.4.1632 Build 20210324, unspecified < 4.3.3.1624 Build 20210416, unspecified < 4.2.6 Build 20210327; QuTS hero: unspecified < h4.5.1.1491 build 20201119 · Fixed: QNAP has already fixed this vulnerability in the following versions:; QTS 4.5.2.1566 Build 20210202 and later; QTS 4.5.1.1495 Build 20201123 and later; QTS 4.3.6.1620 Build 20210322 and later; QTS 4.3.4.1632 Build 20210324 and later; QTS 4.3.3.1624 Build 20210416 and later; QTS 4.2.6 Build 20210327 and later; QuTS hero h4.5.1.1491 build 20201119 and later
- Remediation statusRemediation status changed from Awaiting fix to Patch available.qnap.com ↗
- Before
- Awaiting fix
- After
- Patch available
CVE published
Added to CISA KEV
Fixed release or patch reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.