CVE-2026-22444: Apache Solr: Insufficient file-access checking in standalone core-creation requests

[Jason Gerlowski <gerlowskija () apache org>]

Severity: moderate 

Affected versions:

- Apache Solr 8.6 through 9.10.0

Description:

The "create core" API of Apache Solr 8.6 through 9.10.0 lacks sufficient input validation on some API parameters, which 
can cause Solr to check the existence of and attempt to read file-system paths that should be disallowed by Solr's  
"allowPaths" security setting 
https://https://solr.apache.org/guide/solr/latest/configuration-guide/configuring-solr-xml.html#the-solr-element .  
These read-only accesses can allow users to create cores using unexpected configsets if any are accessible via the 
filesystem.  On Windows systems configured to allow UNC paths this can additionally cause disclosure of NTLM "user" 
hashes. 

Solr deployments are subject to this vulnerability if they meet the following criteria:
  *  Solr is running in its "standalone" mode.
  *  Solr's "allowPath" setting is being used to restrict file access to certain directories.
  *  Solr's "create core" API is exposed and accessible to untrusted users.  This can happen if Solr's  
RuleBasedAuthorizationPlugin 
https://solr.apache.org/guide/solr/latest/deployment-guide/rule-based-authorization-plugin.html  is disabled, or if it 
is enabled but the "core-admin-edit" predefined permission (or an equivalent custom permission) is given to low-trust 
(i.e. non-admin) user roles.

Users can mitigate this by enabling Solr's RuleBasedAuthorizationPlugin (if disabled) and configuring a permission-list 
that prevents untrusted users from creating new Solr cores.  Users should also upgrade to Apache Solr 9.10.1 or 
greater, which contain fixes for this issue.

This issue is being tracked as SOLR-18058 

Credit:

Damon Toey (finder)

References:

https://solr.apache.org
https://www.cve.org/CVERecord?id=CVE-2026-22444
https://issues.apache.org/jira/browse/SOLR-18058