CVSS 3.1
5.9 mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:NCVE-2026-63440
Medium (5.9) in bubka 2fauth. EPSS 0.2% estimated probability of exploitation activity in the next 30 days.
On this page
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.
Severity
- EPSS
- 0.2% estimated probability of exploitation activity in the next 30 days; 10th percentile. Scored 2026-11-10. A forecast for this CVE across the internet, not for your own systems.
- CWEs
- CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
CWE-918 Server-Side Request Forgery (SSRF) - OWASP Top 10
- A01:2025 Broken Access Control
- Published
- NVD analysis
- Awaiting analysis
- Record from
- the NVD, synced
Ask an AI about this CVE
Show the prompt
Explain CVE-2026-63440 for an engineer deciding whether to act. Use https://cve.bz/api/public/cves/CVE-2026-63440?via=ask-ai-copy and https://cve.bz/cve/CVE-2026-63440?via=ask-ai-copy as the source of truth: what is affected and which versions fix it, whether it is in CISA KEV, public exploits, and its EPSS (an internet-wide 30-day estimate of exploitation activity, not a forecast for my systems). If they give no fixed versions, use the CVE record https://cveawg.mitre.org/api/cve/CVE-2026-63440 or the vendor advisory, not third-party mirrors. Tell me how to check whether I am affected and how to verify a fix. Cite the sources and say where they are uncertain.Opens a third-party assistant; its answer is its own, not cve.bz's. The prompt holds only this CVE's id and public links.
Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| Bubka 2FAuth | < 8.0.0 |
Attack patterns (CAPEC)
- CAPEC-664 Server Side Request Forgery Likelihood: High · Severity: High
- CAPEC-27 Leveraging Race Conditions via Symbolic Links Likelihood: Medium · Severity: High
- CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions Likelihood: High · Severity: High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.