CVE-2019-16216: Zulip Server

Medium severity, CVSS 5.4. EPSS: 0.7% chance of exploitation in the next 30 days.

Zulip server before 2.0.5 incompletely validated the MIME types of uploaded files. A user who is logged into the server could upload files of certain types to mount a stored cross-site scripting attack on other logged-in users. On a Zulip server using the default local uploads backend, the attack is only effective against browsers lacking support for Content-Security-Policy such as Internet Explorer 11. On a Zulip server using the S3 uploads backend, the attack is confined to the origin of the configured S3 uploads hostname and cannot reach the Zulip server itself.

Affected products

• Zulip Zulip Server: from 1.8.0, before 2.0.5 (fixed in 2.0.5)

Published 2019-09-18. Last modified 2026-06-17.