CVE-2021-21428

### Impact On Unix like systems, the system's temporary directory is shared between all users on that system. A collocated user can observe the process of creating a temporary sub directory in the shared temporary directory and race to complete the creation of the temporary subdirectory. This vulnerability is local privilege escalation because the contents of the outputFolder can be appended to by an attacker. As such, code written to this directory, when executed can be attacker controlled. openapi-generator-online creates insecure temporary folders with `File.createTempFile` during the code generation process. The insecure temporary folders store the auto-generated files which can be read and appended to by any users on the system. ### Vulnerable Code https://github.com/OpenAPITools/openapi-generator/blob/c6530519975341d7784a252132b2f0854f488901/modules/openapi-generator-online/src/main/java/org/openapitools/codegen/online/service/Generator.java#L184-L187 This vulnerability exists due to a race condition between the deletion of the randomly generated temporary file and the creation of the temporary directory. ```java File outputFolder = File.createTempFile("codegen-", "-tmp"); // Attacker knows the full path of the file that will be generated // delete the file that was created outputFolder.delete(); // Attacker sees file is deleted and begins a race to create their own directory before the code generator // and make a directory of the same name // SECURITY VULNERABILITY: Race Condition! - Attacker beats the code generator and now owns this directory outputFolder.mkdir(); ``` ### Patches The issue has been patched by changing the underlying logic to use `Files.createTempFile` and has been released in the v5.1.0 stable version. This vulnerability has the same root cause as CVE-2021-21363 from the `swagger-api/swagger-codegen` project as this project and that one both share the same original source tree. See: https://github.com/swagger-api/swagger-codegen/security/advisories/GHSA-pc22-3g76-gm6j ### For more information If you have any questions or comments about this advisory: * Open an issue in [OpenAPI Generator Github repo](https://github.com/openAPITools/openapi-generator/) * Email us at [security@openapitools.org](mailto:security@openapitools.org)