CVE-2026-63440

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.

• CWE-367
• CWE-918

• https://github.com/Bubka/2FAuth/commit/52e9db94f2da2a6231d77c49537d6d88ce948ee1
• https://github.com/Bubka/2FAuth/releases/tag/v8.0.0
• https://github.com/Bubka/2FAuth/security/advisories/GHSA-22mh-gmrh-gpwg

Published

Nov 6, 2026

Last Modified

Nov 6, 2026

Status

Received

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