Security readout for executives and security teams
Plain-English summary
Synology SSL VPN Client stored a password/PIN insecurely before version 1.4.5-0684. A remote attacker could access or influence the user’s PIN, but user interaction is required. Business risk is unauthorized VPN configuration and possible interception of later VPN traffic.
Executive priority
Treat as a high-priority endpoint VPN client update. The issue can affect confidentiality and integrity of VPN access, but current provided sources do not confirm active exploitation.
Technical view
CVE-2021-47961 is a CWE-256 plaintext password storage issue in Synology SSL VPN Client versions before 1.4.5-0684. CVSS 3.1 is 8.1: network-accessible, low complexity, no privileges required, user interaction required, with high confidentiality and integrity impact and no availability impact.
Likely exposure
Organizations using Synology SSL VPN Client versions earlier than 1.4.5-0684 are potentially exposed, especially where users connect to sensitive VPN environments.
Exploitation context
The CVE record does not indicate CISA KEV listing, and the provided sources do not report active exploitation. Exploitation requires user interaction and may enable unauthorized VPN configuration or later traffic interception.
Researcher notes
Key constraints are user interaction and no availability impact. The main exposure is insecure local storage enabling PIN access or influence, with downstream VPN configuration and traffic risks. Provided evidence does not include exploit details or telemetry.
Mitigation direction
- Upgrade Synology SSL VPN Client to version 1.4.5-0684 or later.
- Review Synology advisory Synology-SA-26:05 for current vendor guidance.
- Prioritize users with access to sensitive internal networks.
- Consider rotating affected VPN credentials or PINs after client remediation.
Validation and detection
- Inventory installed Synology SSL VPN Client versions.
- Identify clients running versions earlier than 1.4.5-0684.
- Confirm remediation against Synology advisory Synology-SA-26:05.
- Review VPN configuration changes for unexpected modifications.
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
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ATT&CK lookup starting points
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CWE-256: Exact CWE lookup
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Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-47961 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
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:N/UI:R/S:U/C:H/I:H/A:N2.85.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- Synology-SA-26:05 Synology SSL VPN ClientCVE reference · vendor-advisory
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.