CVE-2021-21363

swagger-codegen is an open-source project which contains a template-driven engine to generate documentation, API clients and server stubs in different languages by parsing your OpenAPI / Swagger definition. In swagger-codegen before version 2.4.19, 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. For more details refer to the referenced GitHub Security Advisory. This vulnerability is fixed in version 2.4.19. Note this is a distinct vulnerability from CVE-2021-21364.

swagger-codegen is an open-source project which contains a template-driven engine to generate documentation, API clients and server stubs in different languages by parsing your OpenAPI / Swagger definition. In swagger-codegen before version 2.4.19, 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. For more details refer to the referenced GitHub Security Advisory. This vulnerability is fixed in version 2.4.19. Note this is a distinct vulnerability from CVE-2021-21364.

### 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. #### Java Code The method `File.createTempFile` from the JDK is vulnerable to this local information disclosure vulnerability. https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-generator/src/main/java/io/swagger/generator/online/Generator.java#L174-L185 ### Patches Fix has been applied to the master branch with: * https://github.com/swagger-api/swagger-codegen/commit/987ea7a30b463cc239580d6ad166c707ae942a89 included in release: 2.4.19 ### References * [CWE-378: Creation of Temporary File With Insecure Permissions](https://cwe.mitre.org/data/definitions/378.html) * [CWE-379: Creation of Temporary File in Directory with Insecure Permissions](https://cwe.mitre.org/data/definitions/379.html) ### For more information If you have any questions or comments about this advisory: * Email us at [security@swagger.io](mailto:security@swagger.io) #### Original vulnerability report > I'm performing OSS security research under the GitHub Security Lab Bug Bounty program. > I've been using a custom CodeQL query to find local temporary directory vulnerabilities in OSS with three custom CodeQL queries. > > - https://github.com/github/codeql/pull/4388/files#diff-71d36c0f2bd0b08e32866f873f1c906cdc17277e0ad327c0c6cd2c882f30de4f > - https://github.com/github/codeql/pull/4388/files#diff-1893a18a8bf43c011d61a7889d0139b998a5a78701a30fe7722eddd4c506aaac > - https://github.com/github/codeql/pull/4473 > > The code generated by the Swagger Generator contains a local information disclosure vulnerability. The system temporary directory, on unix-like systems is shared between multiple users. Information written to this directory, or directories created under this directory that do not correctly set the posix standard permissions can have these directories read/modified by other users. > > --- > > This vulnerability exists in the maven plugin. > > This vulnerability is distinctly different. This vulnerability is most likely a local privilege escalation vulnerability. > > https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-generator/src/main/java/io/swagger/generator/online/Generator.java#L174-L185 > > This vulnerability is very similar to this similar vulnerability I disclosed in the Eclipse Jetty project. > > https://github.com/eclipse/jetty.project/security/advisories/GHSA-g3wg-6mcf-8jj6 > > This is due to a race condition between the call to `delete` and the call to `mkdirs`. > > ```java > // ensure file will always be unique by appending random digits > 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 Swagger Code Generator. > // and make a directory of the same name > // SECURITY VULNERABILITY: Race Condition! - Attacker beats Swagger Code Generator and now owns this directory > outputFolder.mkdirs(); > ``` > > 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. > > The fix here is to switch to the `Files` API for creating temporary directories. Which does not contain this race condition, and appropriately sets the correct file permissions. >

### 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. #### Java Code The method `File.createTempFile` from the JDK is vulnerable to this local information disclosure vulnerability. https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-generator/src/main/java/io/swagger/generator/online/Generator.java#L174-L185 ### Patches Fix has been applied to the master branch with: * https://github.com/swagger-api/swagger-codegen/commit/987ea7a30b463cc239580d6ad166c707ae942a89 included in release: 2.4.19 ### References * [CWE-378: Creation of Temporary File With Insecure Permissions](https://cwe.mitre.org/data/definitions/378.html) * [CWE-379: Creation of Temporary File in Directory with Insecure Permissions](https://cwe.mitre.org/data/definitions/379.html) ### For more information If you have any questions or comments about this advisory: * Email us at [security@swagger.io](mailto:security@swagger.io) #### Original vulnerability report > I'm performing OSS security research under the GitHub Security Lab Bug Bounty program. > I've been using a custom CodeQL query to find local temporary directory vulnerabilities in OSS with three custom CodeQL queries. > > - https://github.com/github/codeql/pull/4388/files#diff-71d36c0f2bd0b08e32866f873f1c906cdc17277e0ad327c0c6cd2c882f30de4f > - https://github.com/github/codeql/pull/4388/files#diff-1893a18a8bf43c011d61a7889d0139b998a5a78701a30fe7722eddd4c506aaac > - https://github.com/github/codeql/pull/4473 > > The code generated by the Swagger Generator contains a local information disclosure vulnerability. The system temporary directory, on unix-like systems is shared between multiple users. Information written to this directory, or directories created under this directory that do not correctly set the posix standard permissions can have these directories read/modified by other users. > > --- > > This vulnerability exists in the maven plugin. > > This vulnerability is distinctly different. This vulnerability is most likely a local privilege escalation vulnerability. > > https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-generator/src/main/java/io/swagger/generator/online/Generator.java#L174-L185 > > This vulnerability is very similar to this similar vulnerability I disclosed in the Eclipse Jetty project. > > https://github.com/eclipse/jetty.project/security/advisories/GHSA-g3wg-6mcf-8jj6 > > This is due to a race condition between the call to `delete` and the call to `mkdirs`. > > ```java > // ensure file will always be unique by appending random digits > 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 Swagger Code Generator. > // and make a directory of the same name > // SECURITY VULNERABILITY: Race Condition! - Attacker beats Swagger Code Generator and now owns this directory > outputFolder.mkdirs(); > ``` > > 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. > > The fix here is to switch to the `Files` API for creating temporary directories. Which does not contain this race condition, and appropriately sets the correct file permissions. >

swagger-codegen es un proyecto de código abierto que contiene un motor basado en plantillas para generar documentación, clientes API y stubs de servidor en diferentes idiomas mediante el análisis de su definición de OpenAPI/Swagger. En swagger-codegen versiones anteriores a 2.4.19, en sistemas similares a Unix, el directorio temporal del sistema se comparte entre todos los usuarios de ese sistema. Un usuario ubicado puede observar el proceso de creación de un subdirectorio temporal en el directorio temporal compartido y una corrida para completar la creación del subdirectorio temporal. Esta vulnerabilidad es una escalada de privilegios local porque un atacante puede agregar el contenido de "outputFolder". Como tal, el código escrito en este directorio, cuando se ejecuta, puede ser controlado por el atacante. Para mayor detalles, consulte el GitHub Security Advisory al que se hace referencia. Esta vulnerabilidad es corregido en versión 2.4.19