CVE-2026-56020: Webmin HTTP header authentication bypass

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-18 · updated 2026-08-11
Weakness: CWE-290

Description

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 2.202.

Affected products

Webmin: before 2.202 — fixed in 2.202

How to fix

Upgrade to a fixed version: Webmin 2.202. Check the vendor advisory for mitigations.

References

https://github.com/webmin/webmin/releases/tag/2.202
https://raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2026/va-26-169-02.json
https://webmin.com/security/#webmin-prior-to-2202
https://www.cve.org/CVERecord?id=CVE-2026-56020

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