What is CVE-2020-18985?

CVE-2020-18985 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2021-12-15.

How severe is CVE-2020-18985?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Synacor Zimbra Collaboration Suite

CVE-2020-18985

An issue in /domain/service/.ewell-known/caldav of Zimbra Collaboration 8.8.12 allows attackers to redirect users to any arbitrary website of their choosing.

Vulnerability class: Open Redirect

Published 2021-12-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (49.4th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Synacor Zimbra Collaboration Suite — versions 8.8.12

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

github.com/buxu/bug/issues/3 (Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2020-18985?: CVE-2020-18985 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2021-12-15.
How severe is CVE-2020-18985?: Medium severity. CVSS v3 base score is 6.1 out of 10.