CVE-2026-42210 webmin vulnerability
Webmin is a web-based system administration tool for Unix-like servers. Prior to version 2.640, for Webmin accounts that require a second authentication factor (typically TOTP), an attacker with knowledge of the username and password can bypass the 2FA requirement by using Basic authentication. Webmin is a web-based system administration tool for Unix-like servers. As a workaround, apply the patch from commit da18a16c84ae5c0b78cad79609cb0efb174000ec manually.
Browse Authentication Bypass security risksQuick answer
Webmin should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- < 2.640
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-42210 affects Webmin and involves authentication bypass. Successful exploitation may let an attacker bypass an expected login or multi-factor authentication check. Prioritize deployments that process untrusted input, expose the affected feature, or hold sensitive data. Upgrade Webmin to 2.640 or a later vendor-supported fixed release.
- Inventory every deployment, device, package, plugin, container, build, and environment that uses Webmin.
- Compare the installed version with the recorded affected range: < 2.640.
- Upgrade Webmin to 2.640 or a later vendor-supported fixed release.
- Until patched, restrict the affected API or workflow to trusted administrators and enforce an additional access-control layer at the proxy or network boundary.
- Review configuration, roles, tokens, network paths, and exposed endpoints connected to Webmin; remove access that is not required.
- Review authentication, API, audit, and object-change logs for cross-user access, bypassed checks, or unexpected privileged actions.
- If exploitation is suspected, isolate affected assets, preserve evidence, rotate exposed credentials or keys, restore trusted data, and rebuild compromised systems before returning them to service.
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Verify the fix
- Confirm every affected asset now runs the fixed vendor-supported release or has the documented mitigation for CVE-2026-42210 in place.
- Use a safe regression test to confirm the affected authentication bypass path no longer produces the vulnerable behavior.
- Confirm temporary access controls, endpoint restrictions, network blocks, and least-privilege settings remain effective after the update.
- Review post-remediation logs and rerun Fixnx plus the relevant package, dependency, firmware, browser, or product-specific security check.
- Document affected assets, versions, changes, validation evidence, reviewed logs, and any credential rotation, cleanup, or replacement completed.
Related categories
Related security risks
More published guidance from the same primary category.
Trusted references
FAQ
What is affected by CVE-2026-42210?
Webmin versions listed as affected should be reviewed: < 2.640.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.