Security readout for executives and security teams
Plain-English summary
This Synology DSM flaw could let a local, highly privileged user run arbitrary code through synoagentregisterd on systems before DSM 6.2.4-25553. It is not described as remotely exploitable, but the impact is high because successful abuse could affect confidentiality, integrity, and availability.
Executive priority
Treat this as a high-priority patching item for Synology storage infrastructure, especially systems with shared administration or broad local access. It is not evidenced as actively exploited here.
Technical view
CVE-2021-26563 is an incorrect authorization issue, CWE-863, in synoagentregisterd in Synology DiskStation Manager before 6.2.4-25553. CVSS 3.1 is 8.2 with local attack vector, low complexity, high privileges required, no user interaction, changed scope, and high CIA impact.
Likely exposure
Exposure is likely limited to Synology DSM systems running versions before 6.2.4-25553 where a local high-privilege user or process can reach the vulnerable component.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The CVE states arbitrary code execution is possible via unspecified local vectors, so practical exploitability details are incomplete.
Researcher notes
The public description leaves the vectors unspecified. Prioritize version validation, advisory correlation, and privilege-boundary review around synoagentregisterd. Avoid assuming remote exploitation without additional vendor or researcher evidence.
Mitigation direction
- Upgrade affected Synology DSM systems to 6.2.4-25553 or later per vendor guidance.
- Review Synology SA-21-03 for product-specific fixed releases and deployment notes.
- Restrict local administrative access to DSM systems until patched.
- Investigate any unsupported or end-of-life DSM installations separately.
Validation and detection
- Inventory Synology DSM versions across all DiskStation assets.
- Flag DSM versions earlier than 6.2.4-25553 as potentially affected.
- Confirm whether synoagentregisterd is present on identified DSM systems.
- Check vendor advisory SA-21-03 for exact applicability and fixed version mapping.
- Review local privileged account usage because the CVSS vector requires high privileges.
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-863: 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-2021-26563 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
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:H/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:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H1.56Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.talosintelligence.com/vulnerability_reports/TALOS-2020-1158CVE reference · x_refsource_MISC
- https://www.synology.com/security/advisory/Synology_SA_21_03CVE 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.
Incorrect Authorization
Incorrect Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.