---
id: "CVE-2026-123621"
page: "https://infrastack.ai/live/CVE-2026-123621"
kind: "vulnerability"
aliases: ["CVE-2026-123621"]
title: "Usermin: email attachment names let remote senders overwrite files, run commands"
severity: "high"
cvss: 8.8
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["email", "runtime", "self-hosted", "usermin", "webmin"]
not_affected_if: ["mailbox-module-disabled", "usermin-not-installed"]
published_at: "2026-11-06T15:17:19+00:00"
first_seen_at: "2026-11-06T15:42:44+00:00"
updated_at: "2026-11-06T15:43:58+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123621", "first_seen_at": "2026-11-06T15:42:44+00:00"}]
exploit_sources: []
---

# Usermin: email attachment names let remote senders overwrite files, run commands

Link for people: https://infrastack.ai/live/CVE-2026-123621 (this .md is for agents)

Usermin through 2.570 fails to sanitize attachment filenames in mailbox/detachall.cgi, so path traversal sequences like ../ write files outside the temporary directory. An unauthenticated attacker who emails a crafted attachment can overwrite files such as ~/.forward when the recipient downloads all attachments, enabling command execution.

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

## How to check

- Check the installed Usermin version, for example with `usermin -v` or the package manager, and compare it to the fixed range in the product data.
- Confirm whether the mailbox/detachall.cgi module is enabled in the Usermin web interface.

## Fix

- Upgrade Usermin past 2.570 to the fixed version; the exact version is unknown from the sources given.

## Timeline

- 2026-11-06T15:42:44+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123621

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/usermin-through-2.570-path-traversal-file-write-via-detachall-cgi
- [fix] Patch: github.com https://github.com/webmin/usermin/commit/cb4614e8319e0932b10533a4d5606debf5f40e14

## From the sources

Usermin through 2.570 contains a path traversal vulnerability in mailbox/detachall.cgi that allows remote unauthenticated attackers to write files outside the temporary directory via unsanitized attachment filenames. Attackers can email attachments with ../ sequences in filenames, and when the recipient downloads all attachments, files like ~/.forward are overwritten, enabling command execution.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_