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Vulnerabilities

Vulnerability · CVE-2026-40875

mailcow: dockerized is an open source groupware/email suite based on docker.

Published Apr 21, 2026 · catalog updated Jun 17, 2026 · mailcow: dockerized is an

Check if you run it

No confirmed exploitation is on record for CVE-2026-40875. EPSS is 0.29%. Act only if a listed version of mailcow: dockerized is an is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (mailcow: dockerized is an).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.0
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.29%
Remediation
Advisory link
Affected products
See sources for product scope

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.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-40875

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-40875. EPSS is 0.29%. Act only if a listed version of mailcow: dockerized is an is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS); CWE-80: Basic XSS. EPSS 0.29%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Docker security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Apr 21, 2026 · NIST NVD

    Detected

    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 Log

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 Log

Sources

  • CVE.orgVulnerability recordCVE-2026-40875

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-40875

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-40875

    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 head

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.