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Vulnerability record · CVE-2026-40871 · published 21 April 2026

CVE-2026-40871: Improper input validation vulnerability

mailcow: dockerized is an open source groupware/email suite based on docker. Versions prior to 2026-03b have a second-order SQL injection vulnerability in the quarantine_category field via the Mailcow API. The /api/v1/add/mailbox endpoint stores quarantine_category without validation or sanitization. This value is later used by quarantine_notify.py, which constructs SQL queries using unsafe % string formatting instead of parameterized queries. This results in a delayed (second-order) SQL injection when the quarantine notification job executes, allowing an attacker to inject arbitrary SQL. Using a UNION SELECT, sensitive data (e.g., admin credentials) can be exfiltrated and rendered inside quarantine notification emails. Version 2026-03b fixes the vulnerability.

7.2 CVSS 3.1 High EPSS 0.45% · top 63.6% CWE-20 · Improper input validationCWE-89 · SQL injection Deferred
7.2CVSS 3.1 base score
0.45%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
2References
17 Jun 2026Last modified by NVD

Description

mailcow: dockerized is an open source groupware/email suite based on docker. Versions prior to 2026-03b have a second-order SQL injection vulnerability in the quarantine_category field via the Mailcow API. The /api/v1/add/mailbox endpoint stores quarantine_category without validation or sanitization. This value is later used by quarantine_notify.py, which constructs SQL queries using unsafe % string formatting instead of parameterized queries. This results in a delayed (second-order) SQL injection when the quarantine notification job executes, allowing an attacker to inject arbitrary SQL. Using a UNION SELECT, sensitive data (e.g., admin credentials) can be exfiltrated and rendered inside quarantine notification emails. Version 2026-03b fixes the vulnerability.

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

References

LinkTags
https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-r8fq-wrfm-cj2q
https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-r8fq-wrfm-cj2q

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Source: NIST National Vulnerability Database (record CVE-2026-40871), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.