Security readout for executives and security teams
Plain-English summary
Synology DSM versions before 6.2.4-25553 contain a path traversal flaw in a CGI component. A local user could use it to run arbitrary code on the NAS. Business urgency is highest where DSM devices have many users, weak account hygiene, or local accounts exposed through compromised credentials.
Executive priority
Treat as a high-priority NAS maintenance issue, not an internet-scale emergency based on the provided evidence. Patch affected DSM systems promptly because a compromised local account could become full device compromise.
Technical view
CVE-2021-29088 is CWE-22 in Synology DSM before 6.2.4-25553. The CVSS 3.1 vector is AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, meaning authenticated local access is required, but successful exploitation can fully compromise confidentiality, integrity, and availability.
Likely exposure
Exposure is limited to Synology DSM before 6.2.4-25553, especially systems where local users can authenticate. The source bundle does not identify specific models, packages, or affected build ranges beyond DSM before that version.
Exploitation context
The provided sources do not show CISA KEV listing or confirmed active exploitation. The CVE describes unspecified vectors, so researchers should avoid assuming remote reachability or a known public exploit from this bundle alone.
Researcher notes
Important details are not disclosed in the provided CVE text: vectors are unspecified, CPEs are absent, and affected versions are broad. Base analysis on the vendor advisory and validate against real DSM build numbers.
Mitigation direction
- Update Synology DSM to 6.2.4-25553 or later.
- Review Synology advisory SA-21-03 for product-specific guidance.
- Remove unnecessary local DSM accounts.
- Restrict administrative access to trusted users only.
- Monitor local account activity on unpatched DSM systems.
Validation and detection
- Inventory Synology DSM systems and record exact build numbers.
- Flag DSM versions earlier than 6.2.4-25553.
- Confirm whether local users can access each affected system.
- Check whether SA-21-03 remediation is applied.
- Review logs for unusual local account activity.
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-22: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. 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 lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-29088 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
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/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:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 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.
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.