Self-XSS Vulnerability in Mailcow: Dockerized Email Suite
CVE-2026-40875

7HIGH

Key Information:

Vendor

Mailcow

Status
Mailcow-dockerized
Vendor
CVE Published:
21 April 2026

What is CVE-2026-40875?

A Self-XSS vulnerability exists in Mailcow: Dockerized due to the login history feature rendering the client IP from logs without proper HTML escaping. This flaw arises from the server's trust in the X-Real-IP header, which allows an attacker to inject malicious HTML or JavaScript. This could enable potential exploitation through a Login CSRF attack, giving attackers access to the victim's account and their email through a previous browser tab. It is crucial for users to update to version 2026-03b to mitigate this vulnerability.

Affected Version(s)

mailcow-dockerized < 2026-03b

References

https://github.com/mailcow/mailcow-dockerized/security/ad...
x_refsource_CONFIRM

CVSS V4

Score:
7
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
High
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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