CVE-2020-26250Medium· 6.3▾ SunlitBase class whitelist configuration ignored in OAuthenticator
▾ Sunlit zone — Low / medium · no exploitation signal
impact 34.7 · likelihood 0.2 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 8.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
1.1%
1.1% → 1.1%
What goes wrong?
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.
Who is impacted?
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.
c.Authenticator.whitelist = ... with c.Authenticator.allowed_users = ... avoids the issue.If any users have been authorized during this time who should not have been, they must be deleted via the API or admin interface, per the documentation.
Replacing c.Authenticator.whitelist = ... with c.Authenticator.allowed_users = ... avoids the issue.
In the jupyterhub helm chart prior to 0.10.6, this can be done via hub.extraConfig:
auth:
allowedUsers:
- user1
- user2
hub:
extraConfig:
allowedUsers: |
# set new field not exposed in helm chart < 0.10.6
set_config_if_not_none(c.Authenticator, "allowed_users", "auth.allowedUsers")
If you have any questions or comments about this advisory:
oauthenticator >= 0.12.0, < 0.12.2Upgrade to a patched release:
oauthenticator 0.12.2Connected by shared product, vendor, weakness, or advisory.
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