Reported in SOLR-14515 (private) and fixed in SOLR-14561 (public), released in Solr version 8.6.0. The Replication handler ( https://lucene.apache.org/solr/guide/8_6/index-replication.html#http-api-commands-for-the-replicationhandler) allows commands backup, restore and deleteBackup. Each of these take a location parameter, which was not validated, i.e you could read/write to any location the solr user can access.
On a windows system SMB paths such as \\10.0.0.99\share\folder may also be used, leading to: * The possibility of restoring another SolrCore from a server on the network (or mounted remote file system) may lead to: ** Exposing search index data that the attacker should otherwise not have access to ** Replacing the index data entirely by loading it from a remote file system that the attacker controls * Launching SMB attacks which may result in: ** The exfiltration of sensitive data such as OS user hashes (NTLM/LM hashes), ** In case of misconfigured systems, SMB Relay Attacks which can lead to user impersonation on SMB Shares or, in a worse-case scenario, Remote Code Execution The solution implemented to address these issues was to: * Restrict the location parameter to trusted paths * Prevent remote connection when using Windows UNC Paths ~ David Smiley Apache Lucene/Solr Search Developer http://www.linkedin.com/in/davidwsmiley