CVE-2026-56020
Published: 18 June 2026
Summary
CVE-2026-56020 is a critical-severity Authentication Bypass by Spoofing (CWE-290) vulnerability in Githubusercontent (inferred from references). Its CVSS base score is 9.2 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Forge Web Credentials (T1606); ranked at the 20.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-37909
Vulnerability details
The Webmin HTTP server (miniserv.pl) allows unauthenticated attackers to impersonate any user with a configured SSL client certificate by sending a forged HTTP header. A remote attacker can spoof certificate DNs and authenticate as any user. Fixed in 2.641.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability enables spoofing of SSL client certificate DNs via forged headers to bypass authentication, directly facilitating T1606 Forge Web Credentials.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Reveals spoofed logon attempts through unexpected previous logon timestamps upon legitimate login.
Training specifically addresses recognizing spoofed communications and phishing that enable authentication bypass.
Requiring verifiable identity evidence at appropriate assurance levels makes it substantially harder for attackers to successfully spoof or impersonate users to obtain accounts.
Unique device authentication makes successful spoofing of device identity substantially more difficult to achieve.
Unique identification of non-organizational users reduces the feasibility of authentication bypass by spoofing.
Unique identification and authentication of services before communications makes spoofing of service identities substantially harder.
Isolated trusted path ensures the user interacts only with genuine system components, preventing spoofing of authentication interfaces or prompts.
Directly counters DNS response spoofing by requiring cryptographic origin authentication artifacts from the authoritative source.