Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 1.59% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2022
CVE-2021-44052High confidence
Arbitrary file read
QNAP Systems Inc. · QuTScloud
6.5MediumCVSS 3.1
Scheduled
Patch availableMedium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityMedium→Operational priority:Medium, 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.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs QNAP Systems Inc. QuTScloud 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.
Medium technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Patch available01
What, why and how
An improper link resolution before file access ('Link Following') vulnerability has been reported to affect QNAP device running QuTScloud, QuTS hero, and QTS. If exploited, this vulnerability allows remote attackers to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. We have already fixed this vulnerability in the following versions of QuTScloud, QuTS hero, and QTS: QuTScloud c5.0.1.1998 and later QuTS hero h4.5.4.1971 build 20220310 and later QuTS hero h5.0.0.1986 build 20220324 and later QTS 4.3.4.1976 build 20220303 and later QTS 4.3.3.1945 build 20220303 and later QTS 4.2.6 build 20220304 and later QTS 4.3.6.1965 build 20220302 and later QTS 5.0.0.1986 build 20220324 and later QTS 4.5.4.1991 build 20220329 and later
What
An improper link resolution before file access ('Link Following') vulnerability has been reported to affect QNAP device running QuTScloud, QuTS hero, and QTS. If exploited, this vulnerability allows remote attackers to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. We have already fixed this vulnerability in the following versions of QuTScloud, QuTS hero, and QTS: QuTScloud c5.0.1.1998 and later QuTS hero h4.5.4.1971 build 20220310 and later QuTS hero h5.0.0.1986 build 20220324 and later QTS 4.3.4.1976 build 20220303 and later QTS 4.3.3.1945 build 20220303 and later QTS 4.2.6 build 20220304 and later QTS 4.3.6.1965 build 20220302 and later QTS 5.0.0.1986 build 20220324 and later QTS 4.5.4.1991 build 20220329 and later
Why
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
An improper link resolution before file access ('Link Following') vulnerability has been reported to affect QNAP device running QuTScloud, QuTS hero, and QTS. If exploited, this vulnerability allows remote attackers to traverse the file system to unintended locations and read or overwrite the contents of unexpected files. We have already fixed this vulnerability in the following versions of QuTScloud, QuTS hero, and QTS: QuTScloud c5.0.1.1998 and later QuTS hero h4.5.4.1971 build 20220310 and later QuTS hero h5.0.0.1986 build 20220324 and later QTS 4.3.4.1976 build 20220303 and later QTS 4.3.3.1945 build 20220303 and later QTS 4.2.6 build 20220304 and later QTS 4.3.6.1965 build 20220302 and later QTS 5.0.0.1986 build 20220324 and later QTS 4.5.4.1991 build 20220329 and later
Why
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
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 Link Resolution Before File Access ('Link Following') → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- 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-59 ↗
CWE-59: Improper Link Resolution Before File Access ('Link Following'). The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
- 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:L/UI:N/S:U/C:H/I:N/A:NCommon 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.PRLowPrivileges required: The attacker needs basic user-level 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.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
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
- QuTScloud: unspecified < c5.0.1.1998
- QuTS hero: unspecified < h4.5.4.1971 build 20220310, unspecified < h5.0.0.1986 build 20220324
- QTS: unspecified < 4.3.4.1976 build 20220303, unspecified < 4.3.3.1945 build 20220303, unspecified < 4.2.6 build 20220304, unspecified < 4.3.6.1965 build 20220302, unspecified < 5.0.0.1986 build 20220324, unspecified < 4.5.4.1991 build 20220329
- Fixed
- We have already fixed this vulnerability in the following versions of QuTScloud, QuTS hero, and QTS:
- QuTScloud c5.0.1.1998 and later
- QuTS hero h4.5.4.1971 build 20220310 and later
- QuTS hero h5.0.0.1986 build 20220324 and later
- QTS 4.3.4.1976 build 20220303 and later
- QTS 4.3.3.1945 build 20220303 and later
- QTS 4.2.6 build 20220304 and later
- QTS 4.3.6.1965 build 20220302 and later
- QTS 5.0.0.1986 build 20220324 and later
- QTS 4.5.4.1991 build 20220329 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 5 May 2022 · Last source change 16 Sept 2024, 22:56 UTC · CWE-59 · Improper Link Resolution Before File Access ('Link Following')
CVE recordCVE.org · 5.1
CVSS sourceCNA
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-2021-30911
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.
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.