# CVE-2026-63441: 2FAuth: SSRF guard misses IPv6 NAT64 prefixes, allowing image fetch to reach internal/metadata targets

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. From 6.1.0 until 8.0.0, App\Services\Traits\ValidatesUrls::isPublicIp() does not recognize the 64:ff9b::/96 and 64:ff9b:1::/48 NAT64 prefixes, so an otpauth URI image parameter can pass an IPv6 literal or DNS64-synthesized address whose embedded IPv4 target is private, link-local, loopback, or cloud metadata. In a deployment with image fetching enabled and a NAT64 translation path to the internal IPv4 target, an account holder can submit the crafted URI directly, or an external attacker can induce a victim to import a crafted URI or migration payload. IconService::buildFromRemoteImage() then issues an HTTP GET to the embedded target, allowing image-shaped responses to be recovered or other endpoints to be probed blindly. This issue is fixed in version 8.0.0.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Bubka / 2FAuth: >= 6.1.0, < 8.0.0 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 4.0: 4.9 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:N/SA:N; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-918

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/Bubka/2FAuth/security/advisories/GHSA-wc8m-7c5g-xrrc (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/Bubka/2FAuth/commit/df19e7533082671ecc2e0c735adcd51e93b1cb4c (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/Bubka/2FAuth/releases/tag/v8.0.0 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-63441; retrieved 2026-11-06; source updated 2026-11-06

Revision: 33d358bd5df42e8b1debb7384c1d39af0889cc34caf58637779a3bba2a768574

Canonical: https://y2.dev/cve/CVE-2026-63441

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