CVE-2026-63440: medium-severity vulnerability in Bubka 2FAuth
2FAuth: Authenticated SSRF via DNS rebinding in the otpauth image= icon fetch (validate-then-fetch TOCTOU)
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
10Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.9
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.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
Affected products
Bubka · 2FAuthRelated CVEs — Bubka 2FAuth
In the same product, most dangerous first.
CVE-2024-52598HIGH2FAuth vulnerable to Server Side Request Forgery + URI validation bypass in 2fauth /api/v1/twofaccounts/previewEPSS 0.6%CVE-2026-32133HIGH2FAuth has Blind SSRF in image parameter allows internal network access and moreEPSS 0.6%CVE-2023-36816MEDIUMCross-Site Scripting (XSS) at Account creation in 2FAuthEPSS 0.5%CVE-2024-52597MEDIUM2FAuth vulnerable to stored cross-site scripting via SVG upload and direct access renderEPSS 0.4%CVE-2026-63439CRITICAL2FAuth: Reverse Proxy Guard Trusts Client-Supplied Headers Without Proxy VerificationEPSS —CVE-2026-63438CRITICAL2FAuth: Reverse Proxy Guard Auto-Creates Users With Admin Promotion From Unauthenticated Header ValueEPSS —