# CVE-2026-40871: mailcow: dockerized vulnerable to Second Order SQL Injection in quarantine category via API

> Attackers can inject SQL via the API to exfiltrate sensitive data like admin credentials through delayed quarantine notifications.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Apr 2026
- **Updated:** 21 Apr 2026
- **Also known as:** GHSA-r8fq-wrfm-cj2q

## What is CVE-2026-40871?

CVE-2026-40871 is a high-severity SQL injection vulnerability in mailcow-dockerized, published on 21 Apr 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official 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.

Weakness: CWE-89 (Improper Neutralization of Special Elements used in an SQL Command), CWE-564 (Use of Hibernate with HQL/SQL Query String Containing External Input), CWE-20 (Improper Input Validation), CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-40871?


## How do I fix CVE-2026-40871?

No fix has been published for CVE-2026-40871 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-40871 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40871 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40871 and fix it if it is affected.

What it is: CVE-2026-40871 is a high-severity SQL injection vulnerability in mailcow-dockerized, published on 21 Apr 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40871 exists.

Affected product: mailcow-dockerized. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40871/ (Markdown: https://insights.sbomify.com/CVE-2026-40871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40871
- OSV: https://osv.dev/vulnerability/CVE-2026-40871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40871/
Summaries are generated and may contain mistakes; the official description above is the record.