Security readout for executives and security teams
Plain-English summary
Synology Download Station before 3.8.16-3566 has a critical privilege management flaw. A remote user who can authenticate may be able to run arbitrary code through the CGI component. For executives, the urgent issue is that a low-privilege account on an exposed NAS could become a full compromise path.
Executive priority
Treat as urgent for any NAS running Download Station, especially if reachable from the internet or many users. Prioritize patch verification and access restriction before broader hardening work.
Technical view
CVE-2021-34810 is CWE-269 in Synology Download Station's CGI component. The CVSS 3.1 score is 9.9 with network access, low complexity, low privileges, no user interaction, changed scope, and high confidentiality, integrity, and availability impact. Public details describe unspecified vectors only.
Likely exposure
Exposure is likely where Synology Download Station is installed below 3.8.16-3566 and reachable by authenticated users. Internet-facing NAS portals, shared user accounts, weak credentials, or compromised NAS accounts raise risk materially.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The risk remains high because exploitation requires only network access and a valid low-privilege account, but the public source bundle does not disclose the exact attack vector.
Researcher notes
Public details are limited to improper privilege management in the CGI component with unspecified vectors. Do not assume exploit mechanics beyond authenticated arbitrary code execution. Validation should focus on version state, exposed access paths, and account control.
Mitigation direction
- Update Synology Download Station to 3.8.16-3566 or later.
- Review Synology security advisory SA-21-11 for current vendor guidance.
- Restrict Download Station access to trusted networks and users.
- Remove unused NAS accounts and enforce strong authentication.
- Monitor NAS logs for suspicious authenticated activity.
Validation and detection
- Inventory Synology NAS devices running Download Station.
- Confirm installed Download Station version is at least 3.8.16-3566.
- Check whether Download Station is externally reachable.
- Review user accounts with access to Download Station.
- Verify recent NAS authentication and package activity logs.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-269: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-34810 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H3.16Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.9CriticalVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.synology.com/security/advisory/Synology_SA_21_11CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Privilege Management
Improper Privilege Management represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.