---
id: "CVE-2026-113599"
kind: "vulnerability"
aliases: ["CVE-2026-113599"]
title: "Modoboa: authenticated users can write auto-replies to other mailboxes"
severity: "medium"
cvss: 5.4
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["mail-server", "modoboa", "package", "self-hosted"]
not_affected_if: ["modoboa-2.8.0-or-later", "no-untrusted-accounts"]
published_at: "2026-10-20T16:17:09+00:00"
first_seen_at: "2026-10-23T21:57:20+00:00"
updated_at: "2026-10-25T04:16:32+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-113599", "first_seen_at": "2026-10-23T21:57:20+00:00"}]
---

# Modoboa: authenticated users can write auto-replies to other mailboxes

Modoboa before 2.8.0 has an insecure direct object reference in its auto-reply API: an authenticated user can post to /api/v2/armessages/ with another user's mbox value. An attacker can inject their own auto-reply subject and content into a victim's mailbox settings, or break the victim's auto-reply management with MultipleObjectsReturned errors.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Modoboa version (for example `pip show modoboa` or the version in the deployment's requirements) and see whether it is below `2.8.0`.
- Confirm the auto-reply API is reachable: `POST /api/v2/armessages/` on the Modoboa host.

## Fix

- Upgrade Modoboa to `2.8.0` or later.
- Until upgraded, restrict who can authenticate to the Modoboa web interface and API.

## Timeline

- 2026-10-23T21:57:20+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-113599

## From the sources

Modoboa before 2.8.0 contains an insecure direct object reference vulnerability that allows authenticated users to create auto-reply messages for arbitrary mailboxes by supplying another user's mbox value. Attackers can POST to /api/v2/armessages/ to inject attacker-controlled auto-reply subject and content into victims' settings or break their auto-reply management via MultipleObjectsReturned errors.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_