Vulnerability record · CVE-2026-40875 · published 21 April 2026

CVE-2026-40875: Cross-site scripting vulnerability

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.

7.0 CVSS 4.0 High EPSS 0.29% · top 80.6% CWE-79 · Cross-site scriptingCWE-80 · CWE-80 Deferred

7.0CVSS 4.0 base score

0.29%EPSS exploitation probability, 30 days

NoNot in CISA KEV

0Affected product versions listed by NVD

2References

17 Jun 2026Last modified by NVD

Description

CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

Link	Tags
https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jprq-w83q-q62h
https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-jprq-w83q-q62h

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Source: NIST National Vulnerability Database (record CVE-2026-40875), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.