QNAP NAS Improper Authorization
CVE-2021-28799 is a critical-severity improper authorization vulnerability in HBS 3 from QNAP, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions v16.0.0415, v3.0.210412, v3.0.210411 as the first without the flaw, so updating HBS 3 to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on March 31, 2022, which means attacks have been observed in the wild, including in ransomware campaigns.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update HBS 3 to v16.0.0415 or v3.0.210412 or v3.0.210411 or v16.0.0419, whichever matches your release line, or a later version.
- Update Hybrid Backup Sync to 16.0.0415 or 3.0.210412 or 3.0.210411 or 16.0.0419, whichever matches your release line, or a later version.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on qnap.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| QNAP | HBS 3 | before v16.0.0415; before v3.0.210412; before v3.0.210411; before v16.0.0419 | v16.0.0415, v3.0.210412, v3.0.210411, v16.0.0419 |
| QNAP | HBS 2 | Not specified in the record | Not stated |
| QNAP | HBS 1.3 | Not specified in the record | Not stated |
| QNAP | Hybrid Backup Sync | before 16.0.0415; before 3.0.210412; before 3.0.210411; before 16.0.0419 | 16.0.0415, 3.0.210412, 3.0.210411, 16.0.0419 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 10.0 | Critical | CNA (qnapsecurity.com.tw) |
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 2.0 | 7.5 | High | NVD |
Official description
An improper authorization vulnerability has been reported to affect QNAP NAS running HBS 3 (Hybrid Backup Sync. ) If exploited, the vulnerability allows remote attackers to log in to a device. This issue affects: QNAP Systems Inc. HBS 3 versions prior to v16.0.0415 on QTS 4.5.2; versions prior to v3.0.210412 on QTS 4.3.6; versions prior to v3.0.210411 on QTS 4.3.4; versions prior to v3.0.210411 on QTS 4.3.3; versions prior to v16.0.0419 on QuTS hero h4.5.1; versions prior to v16.0.0419 on QuTScloud c4.5.1~c4.5.4. This issue does not affect: QNAP Systems Inc. HBS 2 . QNAP Systems Inc. HBS 1.3 .
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Authorization
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
How developers prevent this class of flaw
- Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
- Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework and the OWASP ESAPI Access Control feature.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-28799US Government Resource
Other vulnerabilities in HBS 3
- 9.8 Critical severity
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