What is CVE-2017-15891?

CVE-2017-15891 is a medium-severity vulnerability in Synology Calendar, classified under Improper Access Control. CVSS score: 6.5/10. Published 2017-12-08.

How severe is CVE-2017-15891?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Synology Calendar

CVE-2017-15891

Improper access control vulnerability in SYNO.Cal.EventBase in Synology Calendar before 2.0.1-0242 allows remote authenticated users to modify calendar event via unspecified vectors.

Published 2017-12-08 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.

EPSS exploit prediction

EPSS: 0.010 (62.7th percentile), scored 2026-10-07.

Low probability of exploitation in the next 30 days, but still tracked. 63rd percentile — 62.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000

Affected products

Synology Calendar
Synology Calendar — versions before 2.0.1-0242

Weakness classification (CWE)

CWE-284 — Improper Access Control

References

www.synology.com/en-global/support/security/Synology_SA_17_68_Calendar (Vendor Advisory)

Frequently asked questions

What is CVE-2017-15891?: CVE-2017-15891 is a medium-severity vulnerability in Synology Calendar, classified under Improper Access Control. CVSS score: 6.5/10. Published 2017-12-08.
How severe is CVE-2017-15891?: Medium severity. CVSS v3 base score is 6.5 out of 10.