CVE-2022-36048: IP address leak via image proxy bypass in Zulip Server

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-08-31 · updated 2026-06-17
Weakness: CWE-436

Description

Zulip is an open-source team collaboration tool with topic-based threading that combines email and chat. When displaying messages with embedded remote images, Zulip normally loads the image preview via a go-camo proxy server. However, an attacker who can send messages could include a crafted URL that tricks the server into embedding a remote image reference directly. This could allow the attacker to infer the viewer’s IP address and browser fingerprinting information. This vulnerability is fixed in Zulip Server 5.6. Zulip organizations with image and link previews [disabled](https://zulip.com/help/allow-image-link-previews) are not affected.

Affected products

zulip: before 5.6 — fixed in 5.6

How to fix

Upgrade to a fixed version: zulip 5.6. Check the vendor advisory for mitigations.

References

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