Security readout for executives and security teams
Plain-English summary
Synology Calendar had an access-control flaw that could let a logged-in remote user change calendar events they should not be able to modify. The public record does not describe the exact vectors or score. Organizations using old Synology Calendar versions should treat this as an integrity and trust issue for shared scheduling data.
Executive priority
Prioritize remediation where Synology Calendar is used for operational scheduling or shared calendars with many users. This is not supported as actively exploited from the provided evidence, but stale affected versions create avoidable integrity risk.
Technical view
CVE-2017-15891 is CWE-284 in SYNO.Cal.EventBase affecting Synology Calendar before 2.0.1-0242. The CVE states remote authenticated users can modify calendar events through unspecified vectors. No CVSS vector, exploit method, or detailed impact scope is included in the provided sources.
Likely exposure
Exposure is limited to deployments running Synology Calendar versions before 2.0.1-0242, especially where untrusted or broad user groups have authenticated calendar access. The sources do not identify affected DSM versions, configurations, or internet exposure requirements.
Exploitation context
The record supports remote authenticated misuse, not unauthenticated compromise. KEV status is false, and the supplied sources do not report active exploitation or public exploit availability. Because vectors are unspecified, validation should focus on version and access review, not exploit reproduction.
Researcher notes
The public CVE data is sparse: it names SYNO.Cal.EventBase, CWE-284, affected versions before 2.0.1-0242, and remote authenticated event modification. It does not provide CVSS, request details, affected configurations, or a verified exploit path.
Mitigation direction
- Upgrade Synology Calendar to 2.0.1-0242 or later, following Synology guidance.
- Restrict calendar access to trusted users until affected systems are updated.
- Review shared calendar permissions for excessive write access.
- Monitor vendor advisories for any additional product-specific guidance.
Validation and detection
- Inventory Synology Calendar installations and record installed package versions.
- Flag any instance running a version before 2.0.1-0242.
- Review authenticated user groups with calendar write or sharing privileges.
- Check calendar audit or change history for unexpected event 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
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-284: 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 lookupCVE-2017-15891 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
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://www.synology.com/en-global/support/security/Synology_SA_17_68_CalendarCVE 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 Access Control
Improper Access Control represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.