---
id: "CVE-2026-63440"
page: "https://infrastack.ai/live/CVE-2026-63440"
kind: "vulnerability"
aliases: ["CVE-2026-63440"]
title: "2FAuth: DNS rebinding lets logged-in users reach internal network addresses"
severity: "medium"
cvss: 5.9
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["2fauth", "laravel", "package", "php", "self-hosted"]
not_affected_if: ["auth-required", "external-image-fetch-disabled"]
published_at: "2026-11-06T21:17:10+00:00"
first_seen_at: "2026-11-06T21:45:08+00:00"
updated_at: "2026-11-06T21:46:47+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63440", "first_seen_at": "2026-11-06T21:45:08+00:00"}]
exploit_sources: []
---

# 2FAuth: DNS rebinding lets logged-in users reach internal network addresses

Link for people: https://infrastack.ai/live/CVE-2026-63440 (this .md is for agents)

2FAuth, a self-hosted two-factor code manager, validates image URL hostnames and then resolves them again for the fetch, so a DNS record can switch to an internal address in between. An authenticated user can use this to make the server request loopback, private-network, link-local or cloud metadata endpoints.

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

## How to check

- Check the installed 2FAuth version; affected releases are those before `8.0.0`.
- Check whether external otpauth image fetching is enabled in the 2FAuth configuration (unknown setting name in the sources).

## Fix

- Upgrade 2FAuth to `8.0.0`.

## Timeline

- 2026-11-06T21:45:08+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-63440

## Documents

- [advisory] Vendor advisory: github.com https://github.com/Bubka/2FAuth/security/advisories/GHSA-22mh-gmrh-gpwg
- [fix] Patch: github.com https://github.com/Bubka/2FAuth/commit/52e9db94f2da2a6231d77c49537d6d88ce948ee1
- [fix] Release notes: github.com https://github.com/Bubka/2FAuth/releases/tag/v8.0.0

## From the sources

2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. Prior to 8.0.0, the otpauth image-fetch path validates a hostname through ValidatesUrls::isExternalHost() and then lets IconService::storeRemoteImage() resolve the same hostname again for the HTTP request. When external otpauth image fetching is enabled, an authenticated user controlling low-TTL authoritative DNS can return a public address during validation and an internal address during the later connection, bypassing the private-address deny list to reach loopback, private-network, link-local, or cloud metadata endpoints. This issue is fixed in version 8.0.0.

---

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