Vulnerability in github.com/authelia/authelia/v4 (CVE-2026-48794)
Summary
Vulnerability in github.com/authelia/authelia/v4 (CVE-2026-48794). Risk of unauthorized operations or information disclosure. Exploitable via a.b.example.com. Mitigation: upgrade to 4.39.20 or later.
Original description
The description as published by the source.
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 p…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-48794 has been found in github.com/authelia/authelia/v4.
Attackers can target a specific entry point like a.b.example.com over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade github.com/authelia/authelia/v4 to 4.39.20 or later.
If unsure, ask your IT team or search "github.com/authelia/authelia/v4 CVE-2026-48794" on the vendor's site.
CVE-2026-48794 (github.com/authelia/authelia/v4) — CWE-178
Attack surface: a.b.example.com / example.com / bypass
Patched: 4.39.20 — apply immediately
Workaround: See the below examples for configurations to avoid.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-178) exists in github.com/authelia/authelia/v4. Attackers reach the vulnerable code path via a.b.example.com.
Check the vendor advisory for the affected versions of github.com/authelia/authelia/v4. Attack surface: a.b.example.com / example.com / bypass.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 4.39.20.
Workaround: See the below examples for configurations to avoid.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/authelia/authelia/v4' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'github.com/authelia/authelia/v4' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/authelia/authelia/v4を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
See the below examples for configurations to avoid.パッチが適用されるまでの応急処置として、See the below examples for configurations to avoid. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade github.com/authelia/authelia/v4 to 4.39.20ステージング環境で 4.39.20 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- web github.com