CVE-2026-40875

7.0 HIGH 0.2% exploit odds Fix listed XSS Browser & mail

What it is

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.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account, but needs a user to act. High risk of data exposure.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-04-21 20:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-26 21:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 7.0 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-04-21 20:17 UTC
Last modified: 2026-10-26 21:10 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Deferred

Attack profile CVSS 4.0 · 7.0

Attack vector: Network
Complexity: High
Attack requirements: Present
Privileges needed: Low
User interaction: Passive
Confidentiality: High
Integrity: None
Availability: None

Raw vector

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:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-40875.md and follow it. Check whether this project is affected by CVE-2026-40875. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record