Authorization Flaw in oauthenticator (CVE-2020-26250)
Summary
Vulnerability in oauthenticator (CVE-2020-26250). Confidential information can be exposed externally. Exploitable via Authenticator.whitelist. Mitigation: upgrade to 0.12.2 or later.
Original description
The description as published by the source.
OAuthenticator is an OAuth login mechanism for JupyterHub. In oauthenticator from version 0.12.0 and before 0.12.2, the deprecated (in jupyterhub 1.2) configuration Authenticator.whitelist, which should be transparently mapped to Authenticator.allowed_users with a warning, is instead ignored by OAuthenticator classes, resulting in the same behavior as if this configuration has not been set. If this is the only mechanism of authorization restriction (i.e. no group or team restrictions in configuration) then all authenticated users will be allowed. Provider-based restrictions, including deprecated values such as GitHubOAuthenticator.org_whitelist are not affected. All users of OAuthenticator 0.12.0 and 0.12.1 with JupyterHub 1.2 (JupyterHub Helm chart 0.10.0-0.10.5) who use the admin.whitelist.users configuration in the jupyterhub helm chart or the c.Authenticator.whitelist configuration directly. Users of other deprecated configuration, e.g. c.GitHubOAuthenticator.team_whitelist are not affected. If you see a log line like this and expect a specific list of allowed usernames: "[I 2020-11-27 16:51:54.528 JupyterHub app:1717] Not using allowed_users. Any authenticated user will be allowed." you are likely affected. Updating oauthenticator to 0.12.2 is recommended. A workaround is to replace the deprecated c.Authenticator.whitelist = ... with c.Authenticator.allowed_users = .... If any users have been authorized during this time who should not have been, t…
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
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-2020-26250 has been found in oauthenticator.
Attackers can target a specific entry point like Authenticator.whitelist over the network to misuse the product.
Confidential information can be exposed externally.
What to do: upgrade oauthenticator to 0.12.2 or later.
If unsure, ask your IT team or search "oauthenticator CVE-2020-26250" on the vendor's site.
CVE-2020-26250 (oauthenticator) — CWE-863
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Authenticator.whitelist / Authenticator.allowed_users / GitHubOAuthenticator.org_whitelist / admin.whitelist.users
Patched: 0.12.2 — 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.
Incorrect authorization (CWE-863) exists in oauthenticator. Attackers reach the vulnerable code path via Authenticator.whitelist.
Check the vendor advisory for the affected versions of oauthenticator. Attack surface: Authenticator.whitelist / Authenticator.allowed_users / GitHubOAuthenticator.org_whitelist / admin.whitelist.users.
Severity: ?. Confidential information can be exposed externally.
Update to 0.12.2.
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 'oauthenticator' . 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 'oauthenticator' . | 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
oauthenticator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 oauthenticator to 0.12.2ステージング環境で 0.12.2 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
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- advisory jupyterhub.readthedocs.io
- package github.com
- patch github.com
- web github.com