Security readout for executives and security teams
Plain-English summary
CVE-2021-47960 affects Synology SSL VPN Client before 1.4.5-0684. A malicious web page could trick a user’s browser into requesting files from the client’s local HTTP server, exposing sensitive installation-directory files such as configurations, certificates, and logs. The main business risk is confidentiality loss, not system takeover.
Executive priority
Treat as a moderate-priority endpoint confidentiality issue. It should be remediated in normal patch cycles, faster for privileged users or systems handling sensitive VPN material. There is no provided evidence of active exploitation.
Technical view
The vulnerability is CWE-552: files or directories accessible to external parties. The client exposes a local HTTP server on loopback; with user interaction, a remote attacker can leverage a crafted web page to retrieve files from the installation directory. CVSS 3.1 is 6.5: network attack vector, low complexity, no privileges, user interaction required, high confidentiality impact.
Likely exposure
Exposure is limited to endpoints running Synology SSL VPN Client versions before 1.4.5-0684. Systems are most at risk when users browse untrusted or attacker-controlled web content while the vulnerable client is installed or active.
Exploitation context
No source provided indicates active exploitation, and this CVE is not listed as KEV in the supplied data. Exploitation requires user interaction with a crafted web page and targets file disclosure through the client’s loopback-bound local HTTP service.
Researcher notes
The key exposure is browser-mediated access to a loopback HTTP service, not direct Internet reachability. Validate affected versions and local service behavior without extracting sensitive files. Public sources do not provide broader affected product details beyond Synology SSL VPN Client before 1.4.5-0684.
Mitigation direction
- Upgrade Synology SSL VPN Client to 1.4.5-0684 or later, following Synology’s advisory.
- Prioritize endpoints used by VPN administrators or users with sensitive certificates or logs.
- If immediate upgrade is not possible, review Synology guidance for supported workarounds.
- Warn users against opening untrusted links until affected clients are updated.
Validation and detection
- Inventory endpoints with Synology SSL VPN Client installed.
- Confirm installed client versions are 1.4.5-0684 or later.
- Review installation directories for sensitive certificates, configurations, and logs.
- Check endpoint and proxy logs for suspicious browsing around VPN client use.
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-552: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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 lookupCVE-2021-47960 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
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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:N/A:N2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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.
Files or Directories Accessible to External Parties
Files or Directories Accessible to External Parties represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.