Vulnerability in github.com/authelia/authelia/v4 (CVE-2026-47203)
Summary
Vulnerability in github.com/authelia/authelia/v4 (CVE-2026-47203). Risk of unauthorized operations or information disclosure. Exploitable via Authorization. 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 4.38.0 through 4.39.19, when a user authenticates via Basic Auth (i.e via the Authorization header with the Basic scheme) on the authz verification endpoint, Authelia takes the username directly from the Authorization header and passes it as is to the regulation system for ban checking and attempt recording. LDAP treats usernames case insensitively : john, John, and JOHN all bind as the same user. But the regulation SQL queries treat the lookup of these values in certain scenarios as case sensitive. This allows each variation of a usernames case to have its own ban bucket. Upgrade to 4.39.20 to receive a patch. As a workaround, explicitly disable the basic auth mechanism.
Source: GitHub Security Advisories (Global) 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-2026-47203 has been found in github.com/authelia/authelia/v4.
Attackers can target a specific entry point like Authorization 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-2026-47203" on the vendor's site.
CVE-2026-47203 (github.com/authelia/authelia/v4) — CWE-178
Attack surface: Authorization / Basic / john / John
Patched: 4.39.20 — apply immediately
Workaround: Explicitly disable the basic auth mechanism.
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 Authorization.
Check the vendor advisory for the affected versions of github.com/authelia/authelia/v4. Attack surface: Authorization / Basic / john / John.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 4.39.20.
Workaround: Explicitly disable the basic auth mechanism.
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
Explicitly disable the basic auth mechanism.パッチが適用されるまでの応急処置として、Explicitly disable the basic auth mechanism. 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