Missing Authentication for Critical Function in RTRR Server in HBS3
Priority MEDIUM 58CWE-284Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-284.
Summary
An improper access control vulnerability has been reported to affect certain legacy versions of HBS 3. If exploited, this vulnerability allows attackers to compromise the security of the operating system.QNAP have already fixed this vulnerability in the following versions of HBS 3: QTS 4.3.6: HBS 3 v3.0.210507 and later QTS 4.3.4: HBS 3 v3.0.210506 and later QTS 4.3.3: HBS 3 v3.0.210506 and later
Why it matters now
EPSS 0.16093 96th percentileScored 2026-11-07
Fix Fixed HBS 3 (QNAP Systems Inc.): v3.0.210507, v3.0.210506
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| QNAP | HBS 3 | before v3.0.210507 | v3.0.210507 | Patch available | CNA |
| QNAP | HBS 3 | before v3.0.210506 | v3.0.210506 | Patch available | CNA |
| QNAP | HBS 3 | before v3.0.210506 | v3.0.210506 | Patch available | CNA |
- HBS 3 VendorQNAP Affected before v3.0.210507 Fixed in v3.0.210507 Patch available CNA
- HBS 3 VendorQNAP Affected before v3.0.210506 Fixed in v3.0.210506 Patch available CNA
- HBS 3 VendorQNAP Affected before v3.0.210506 Fixed in v3.0.210506 Patch available CNA
CPE configurations NVD · 5
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:* | before 3.0.210507 | Vulnerable | QNAP |
| cpe:2.3:o:qnap:qts:4.3.6:-:*:*:*:*:*:* | 4.3.6 | Running on | QNAP |
| cpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:* | before 3.0.210506 | Vulnerable | QNAP |
| cpe:2.3:o:qnap:qts:4.3.4:-:*:*:*:*:*:* | 4.3.4 | Running on | QNAP |
| cpe:2.3:o:qnap:qts:4.3.3:-:*:*:*:*:*:* | 4.3.3 | Running on | QNAP |
- cpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:* Versions before 3.0.210507 Vulnerable ·QNAP
- cpe:2.3:o:qnap:qts:4.3.6:-:*:*:*:*:*:* Versions 4.3.6 Running on ·QNAP
- cpe:2.3:a:qnap:hybrid_backup_sync:*:*:*:*:*:*:*:* Versions before 3.0.210506 Vulnerable ·QNAP
- cpe:2.3:o:qnap:qts:4.3.4:-:*:*:*:*:*:* Versions 4.3.4 Running on ·QNAP
- cpe:2.3:o:qnap:qts:4.3.3:-:*:*:*:*:*:* Versions 4.3.3 Running on ·QNAP
Remediation
- Fix · CNA HBS 3 (QNAP Systems Inc.) Fixed in v3.0.210507
- Fix · CNA HBS 3 (QNAP Systems Inc.) Fixed in v3.0.210506
- Fix · CNA HBS 3 (QNAP Systems Inc.) Fixed in v3.0.210506
Timeline
- 2026-10-02 Threatist record created from CVE-2021-28809
- 2026-10-03 Alias added: GHSA-fwr8-wff7-fmxw
References
More QNAP Hybrid Backup Sync vulnerabilities
- TI-2021-09791 Improper Authorization Vulnerability in HBS 3 (Hybrid Backup Sync) KEVCVSS 3.1CRITICAL 10.0
- TI-2024-33823 Command injection in QNAP HBS 3 Hybrid Backup Sync CVSS 4.0CRITICAL 9.5
- TI-2025-38995 An external control of file name or path vulnerability has been reported to affect HBS 3… CVSS 4.0HIGH 7.0
- TI-2025-38994 Information disclosure through error messages in QNAP HBS 3 Hybrid Backup Sync CVSS 4.0HIGH 7.0
- TI-2024-35893 Buffer overflow in QNAP HBS 3 Hybrid Backup Sync CVSS 4.0MEDIUM 6.3
Sources
- CVE-2021-28809 · CVE Program
- CVE-2021-28809 · NVD
- FIRST EPSS
- GHSA-fwr8-wff7-fmxw · GitHub Advisory Database · CC BY 4.0
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