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TI-2026-86113 Aliases CVE-2026-63440

Server-side request forgery in 2FAuth via DNS rebinding in icon fetch

Priority LOW 26CWE-367Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
High
Impact type
—
Confidentiality · integrity · availability
High · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

2FAuth before 8.0.0 is affected. The otpauth image fetch validates a hostname and then resolves it again for the HTTP request, which is a time-of-check to time-of-use race (CWE-367). When external otpauth image fetching is enabled, an authenticated user who controls a DNS server with low TTLs can return a public address during validation and an internal address during the request, bypassing the private-address deny list to reach loopback, private network, link-local or cloud metadata endpoints (CWE-918).

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

Description from the CNA

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.

Why it matters now

EPSS 0.00202 10th percentileScored 2026-11-07
Fix Fixed 2FAuth (Bubka): 8.0.0

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
Bubka2FAuthbefore 8.0.08.0.0Patch availableCNA
  • 2FAuth VendorBubka Affected before 8.0.0 Fixed in 8.0.0 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:2fauth:2fauth:*:*:*:*:*:*:*:*——Bubka
  • cpe:2.3:a:2fauth:2fauth:*:*:*:*:*:*:*:* Versions — — ·Bubka

Remediation

Upgrade 2FAuth to version 8.0.0 or later, which fixes the issue.

Written with Claude Haiku 5.5 from the sources below · 2026-11-06

  • Fix · CNA 2FAuth (Bubka) Fixed in 8.0.0

Timeline

  1. 2026-11-06 Threatist record created from CVE-2026-63440
  2. 2026-11-08 Priority changed: MEDIUM → LOW

References

Other 3

  • TI-2026-24670 2FAuth has Blind SSRF in image parameter allows internal network access and more CVSS 4.0HIGH 7.8
  • TI-2024-35258 2FAuth vulnerable to Server Side Request Forgery + URI validation bypass in 2fauth /api/v1/twofaccounts/preview CVSS 3.1HIGH 7.5
  • TI-2025-28827 A group deletion race condition in 2FAuth v5.5.0 causes data inconsistencies and orphaned… CVSS 3.1MEDIUM 6.5
  • TI-2024-35257 2FAuth vulnerable to stored cross-site scripting via SVG upload and direct access render CVSS 3.1MEDIUM 6.1
  • TI-2023-18610 Cross-Site Scripting (XSS) at Account creation in 2FAuth CVSS 3.1MEDIUM 6.1
  • TI-2026-86111 Reverse proxy guard in 2FAuth accepts unauthenticated user headers CVSS 3.1CRITICAL 9.8
See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences