CVE-2026-40875

mailcow: dockerized vulnerable to stored XSS in user login history real_rip

HIGH
7
CVSS Score
Published: April 21, 2026 at 07:19 PM UTC
Updated: October 26, 2026 at 09:10 PM UTC
1 product affected across 1 vendorMailcow

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Severity
HIGH7
Exploit prediction
EPSS 0.2%
SSVC
PoC

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2026-03b
Affected range stops below 2026-3b, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCPoCNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7HIGHGitHub_M
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79CWE-80

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