Security readout for executives and security teams
Plain-English summary
This flaw lets a highly privileged, logged-in user on Synology DSM run arbitrary code through PPPoE network settings. It is serious because successful abuse can fully compromise confidentiality, integrity, and availability, but it is not described as unauthenticated or publicly exploited in the provided sources.
Executive priority
Treat this as a high-priority remediation for exposed or business-critical Synology systems. The privilege requirement reduces emergency urgency, but the impact is full system compromise if an attacker obtains or already has high-level DSM access.
Technical view
CVE-2021-29083 is a CWE-78 OS command injection in SYNO.Core.Network.PPPoE in Synology DSM before 6.2.3-25426-3. The vulnerable input is the realname parameter. CVSS 3.1 is 7.2 with network access, low complexity, high privileges required, no user interaction, and high impact.
Likely exposure
Organizations running Synology DSM versions before 6.2.3-25426-3 are potentially exposed, especially where DSM administration is reachable over the network. Practical risk depends on who has high-privilege DSM access and whether management interfaces are exposed beyond trusted networks.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability requires authenticated high privileges, which lowers broad internet wormability but remains important for insider risk, compromised admin accounts, or chained attacks.
Researcher notes
Evidence is limited to the CVE data and Synology advisory reference. Do not assume broader affected products or exploit availability. Focus validation on DSM version, network exposure, privileged account paths, and whether the PPPoE component is present or configured.
Mitigation direction
- Check Synology advisory Synology_SA_20_26 for model-specific fixed releases.
- Update DSM to a fixed release; sources identify versions before 6.2.3-25426-3 as vulnerable.
- Restrict DSM administration to trusted networks or VPN access only.
- Limit high-privilege DSM accounts to users with operational need.
- Review DSM account security, including MFA and credential hygiene where supported.
Validation and detection
- Inventory Synology DSM devices and record exact DSM versions.
- Flag any DSM version earlier than 6.2.3-25426-3 for remediation review.
- Confirm whether DSM management is reachable from untrusted networks.
- Review privileged account membership and recent administrative activity.
- Check logs for unusual PPPoE or network configuration changes.
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-78: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter 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 lookupCVE-2021-29083 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
- 7.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:H/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:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H1.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.2HighVector: CVSS:3.1/AV:N/AC:L/PR:H/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_20_26CVE 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 Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.