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CVE-2026-56020 is an authentication bypass vulnerability in Webmin's HTTP server component, miniserv.pl. The flaw allows a remote unauthenticated attacker to impersonate any user who has a configured SSL client certificate by supplying a forged HTTP header that spoofs the certificate distinguished name (DN). As a result, miniserv.pl can treat attacker-controlled header data as if it originated from a validated client-certificate authentication flow, enabling the attacker to authenticate as another user without possessing that user's certificate. The issue affects Webmin versions prior to 2.641.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An authentication bypass vulnerability in the Webmin HTTP server (miniserv.pl) that allows unauthenticated remote attackers to spoof certificate distinguished names via a forged HTTP header and impersonate any user with a configured SSL client certificate.
An authentication bypass vulnerability in the Webmin HTTP server (miniserv.pl) that allows unauthenticated remote attackers to spoof certificate distinguished names via a forged HTTP header and impersonate any user with a configured SSL client certificate.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.