Open Redirect in authlib (CVE-2026-41479)
Summary
Vulnerability in authlib (CVE-2026-41479). Risk of unauthorized operations or information disclosure. Exploitable via redirect_uri. Mitigation: upgrade to 1.7.1 or later.
Original description
The description as published by the source.
Summary
Authlib's OAuth 2.0 authorization endpoint can be turned into an unauthenticated open redirect when a request uses an unsupported response_type and supplies an attacker-controlled redirect_uri.
The vulnerable behavior happens before client lookup and before any redirect URI validation. As a result, an attacker does not need a valid client registration, an authenticated user, or any prior state. A single request to the authorization endpoint is enough to obtain a 302 Location response to an arbitrary attacker-controlled URL.
It was confirmed that the vulnerable code is present in tag v1.6.6 and in the current HEAD under test (68e6ab3fdfc71a328b1966bad5c6aba0f7d0c2e1, git describe: v1.6.6-104-g68e6ab3f). The issue was dynamically reproduced locally on the current HEAD.
Details
The root cause is that AuthorizationServer.get_authorization_grant() copies the raw request
redirect_uri into an UnsupportedResponseTypeError before any client has been resolved and
before any redirect URI validation has happened:
# authlib/oauth2/rfc6749/authorization_server.py
raise UnsupportedResponseTypeError(
f"The response type '{request.payload.response_type}' is not supported by the server.",
request.payload.response_type,
redirect_uri=request.payload.redirect_uri,
)
That error object is later rendered by OAuth2Error.__call__(). If redirect_uri is set, Authlib
automatically returns a redirect response to that URI:
# authlib/…
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-2026-41479 has been found in authlib.
Attackers can target a specific entry point like redirect_uri over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.4/10.
What to do: upgrade authlib to 1.7.1 or later.
If unsure, ask your IT team or search "authlib CVE-2026-41479" on the vendor's site.
CVE-2026-41479 (authlib) — CWE-601 / CVSS v3 5.4
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: redirect_uri / UnsupportedResponseTypeError
Patched: 1.7.1 — apply immediately
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-601) exists in authlib. Attackers reach the vulnerable code path via redirect_uri without authentication.
Check the vendor advisory for the affected versions of authlib. Attack surface: redirect_uri / UnsupportedResponseTypeError.
Severity: Medium (CVSS 5.4/10). Risk of unauthorized operations or information disclosure.
Update to 1.7.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'authlib' . 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
-
1Identify exposure identify
grep -r 'authlib' . | 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
authlibを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade authlib to 1.7.1ステージング環境で 1.7.1 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。
-
3Post-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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-41479 python-authlib
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com