Title: CVE-2020-13957: The checks added to unauthenticated configset uploads in Apache Solr can be circumvented category: solr/security cve: CVE-2020-13957

Severity: High

Versions Affected: 6.6.0 to 6.6.6 7.0.0 to 7.7.3 8.0.0 to 8.6.2

Description: Solr prevents some features considered dangerous (which could be used for remote code execution) to be configured in a ConfigSet that's uploaded via API without authentication/authorization. The checks in place to prevent such features can be circumvented by using a combination of UPLOAD/CREATE actions.

Mitigation: Any of the following are enough to prevent this vulnerability:

• Disable UPLOAD command in ConfigSets API if not used by setting the system property: configset.upload.enabled to false (see docs)
• Use Authentication/Authorization and make sure unknown requests aren't allowed (see docs)
• Upgrade to Solr 8.6.3 or greater.
• If upgrading is not an option, consider applying the patch in SOLR-14663
• No Solr API, including the Admin UI, is designed to be exposed to non-trusted parties. Tune your firewall so that only trusted computers and people are allowed access

Credit: Tomás Fernández Löbbe, András Salamon

References: SOLR-14925: CVE-2020-13957: The checks added to unauthenticated configset uploads can be circumvented