CVE-2026-40875 mailcow: dockerized vulnerable to stored XSS in user login history real_rip
Attackers can inject scripts into login history via X-Real-IP header, enabling account takeover and email access through CSRF.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-40875?
CVE-2026-40875 is a high-severity cross-site scripting vulnerability in mailcow-dockerized, published on 21 Apr 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the user dashboard's "Seen successful connections" (login history) renders the client IP from login logs without HTML escaping. Because the server trusts the X-Real-IP header as the source IP for logging, an attacker can inject HTML/JS into this field. This Self-XSS can be exploited by a Login CSRF to force the victim into the attacker's account, and then read emails in a previous browser tab. Version 2026-03b fixes the vulnerability.
Which versions are affected by CVE-2026-40875?
How do I fix CVE-2026-40875?
No fix has been published for CVE-2026-40875 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-40875 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40875 exists.
Sources
Also known as GHSA-jprq-w83q-q62h.