Skip to content
Fencer Intel
critical 9.3

CVE-2026-40872 json

mailcow: dockerized vulnerable to stored XSS in autodiscover logs email address field

published 6mo ago modified 14d ago also EUVD-2026-24254

cvss
9.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

mailcow: dockerized is an open source groupware/email suite based on docker. In versions prior to 2026-03b, the admin dashboard's Autodiscover logs render the EMailAddress value (logged as the "user" field) without HTML escaping. By submitting an unauthenticated Autodiscover request with a crafted EMailAddress containing HTML/JS, the payload is stored in Redis and executed when an admin views the Autodiscover logs. Version 2026-03b fixes the vulnerability.

Patch / fix

  • mailcow mailcow:_dockerized 2026-03b

Is CVE-2026-40872 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
total
Assessed
6mo ago

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-f9xf-vc72-rcgm referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:N
CNA 4.0 9.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/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

Affected products

  • mailcow mailcow-dockerized

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.