SSRF in Bubka 2fauth
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.
Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)
Published .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Bubka 2fauth — versions < 8.0.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-63440?
- CVE-2026-63440 is a medium-severity vulnerability in Bubka 2fauth, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 5.9/10. Published 2026-11-06.
- How severe is CVE-2026-63440?
- Medium severity. CVSS v3 base score is 5.9 out of 10.