Apache CouchDB contains an insecure default initialization of resource vulnerability which can allow an attacker to escalate to administrative privileges.

CouchDB version 3.0.0 shipped with a new configuration setting that governs access control to the entire database server called requirevaliduserexceptforup. It was meant as an extension to the long standing setting requirevaliduser, which in turn requires that any and all requests to CouchDB will have to be made with valid credentials, effectively forbidding any anonymous requests. The new requirevaliduserexceptforup is an off-by-default setting that was meant to allow requiring valid credentials for all endpoints except for the /up endpoint. However, the implementation of this made an error that lead to not enforcing credentials on any endpoint, when enabled. CouchDB versions 3.0.1[1] and 3.1.0[2] fix this issue.

CouchDB administrative users before 2.2.0 can configure the database server via HTTP(S). Due to insufficient validation of administrator-supplied configuration settings via the HTTP API, it is possible for a CouchDB administrator user to escalate their privileges to that of the operating system's user under which CouchDB runs, by bypassing the blacklist of configuration settings that are not allowed to be modified via the HTTP API. This privilege escalation effectively allows a CouchDB admin user to gain arbitrary remote code execution, bypassing CVE-2017-12636 and CVE-2018-8007.

Due to differences in the Erlang-based JSON parser and JavaScript-based JSON parser, it is possible in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to submit users documents with duplicate keys for 'roles' used for access control within the database, including the special case 'admin' role, that denotes administrative users. In combination with CVE-2017-12636 (Remote Code Execution), this can be used to give non-admin users access to arbitrary shell commands on the server as the database system user. The JSON parser differences result in behaviour that if two 'roles' keys are available in the JSON, the second one will be used for authorising the document write, but the first 'roles' key is used for subsequent authorization for the newly created user. By design, users can not assign themselves roles. The vulnerability allows non-admin users to give themselves admin privileges.

CouchDB administrative users can configure the database server via HTTP(S). Some of the configuration options include paths for operating system-level binaries that are subsequently launched by CouchDB. This allows an admin user in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to execute arbitrary shell commands as the CouchDB user, including downloading and executing scripts from the public internet.