CVE-2026-48794
Authelia has an Edge Case Access Control Rule Mismatch
Blast Radius
github.com/authelia/authelia/v4Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/authelia/authelia/v4 | ≥ 4.36.0&&< 4.39.20 | 4.39.20 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/authelia/authelia/v4. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/authelia/authelia/v4 to 4.39.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48794 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-48794 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-48794. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-48794 in your dependencies?
O3 detects CVE-2026-48794 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.