Authelia is an open-source authentication and authorization server providing two-factor authentication and single sign-on (SSO) for applications via a web portal. In versions 4.36.0 through 4.39.19, due to lack of canonicalization of domains in very specific edge cases, an access control rule may be skipped when it should match a request. The specific conditions that could lead to a security issue for vulnerability are: 1. The specific target resource of the attack must be using the forwarded authorization integration; 2. The requested domain must have two additional segments compared to a session domain i.e. `a.b.example.com` is requested, but the session domain is `example.com`; 3. There access control rules must specify two separate rules which both contain inexact domain matches such as `*.b.example.com` and `*.example.com` i.e. wildcards, username matches, group matches; 4. The rules must be in order of most specific domain to least specific domain; 5. The second rule must be more permissive than the first rule; 6. The attacker must specifically request a URL for the more specific domain, with the second part containing one or more capitalized letters i.e. `https://a.B.example.com` and no other segment with capitalized letters; 7. The integration used must not be the Envoy ExtAuthz integration; and 8. The proxy must not canonicalize the requested host name in the relevant header before sending it to the relevant authorization endpoint. The kind of configuration used to produce this issue and result in a `bypass` rule being matched has long been highly discouraged. Essentially hosts which should be bypassed entirely should not be secured by having the proxy check them with the authorization handlers. Upgrade to 4.39.20 to receive a patch.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - Authelia is an open-source authentication and authorization server providing two-factor authentication and
    single sign-on (SSO) for applications via a web portal. In versions 4.36.0 through 4.39.19, due to lack of
    canonicalization of domains in very specific edge cases, an access control rule may be skipped when it
    should match a request. The specific conditions that could lead to a security issue for vulnerability are:
    1. The specific target resource of the attack must be using the forwarded authorization integration; 2.
    The requested domain must have two additional segments compared to a session domain i.e. `a.b.example.com`
    is requested, but the session domain is `example.com`; 3. There access control rules must specify two
    separate rules which both contain inexact domain matches such as `*.b.example.com` and `*.example.com`
    i.e. wildcards, username matches, group matches; 4. The rules must be in order of most specific domain to
    least specific domain; 5. The second rule must be more permissive than the first rule; 6. The attacker
    must specifically request a URL for the more specific domain, with the second part containing one or more
    capitalized letters i.e. `https://a.B.example.com` and no other segment with capitalized letters; 7. The
    integration used must not be the Envoy ExtAuthz integration; and 8. The proxy must not canonicalize the
    requested host name in the relevant header before sending it to the relevant authorization endpoint. The
    kind of configuration used to produce this issue and result in a `bypass` rule being matched has long been
    highly discouraged. Essentially hosts which should be bypassed entirely should not be secured by having
    the proxy check them with the authorization handlers. Upgrade to 4.39.20 to receive a patch.
    (CVE-2026-48794)

ID	Name	Product	Family	Type	Severity
444048	SCA: security update for github.com/authelia/authelia/v4 (GHSA-j748-h363-wqj8)	Tenable Cloud Security	SCA Checks	Local	low
444048	SCA: security update for github.com/authelia/authelia/v4 (GHSA-j748-h363-wqj8)	Tenable Self-Hosted Container Security	SCA Checks	Local	low

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CVE-2026-48794

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