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OpenAPI-Generator online generator: Local Privilege Escalation Vulnerability via System Temp Directory

Critical
wing328 published GHSA-23x4-m842-fmwf May 10, 2021

Package

maven openapi-generator-online.jar (Maven)

Affected versions

< 5.1.0

Patched versions

5.1.0

Description

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

File outputFolder = File.createTempFile("codegen-", "-tmp");
outputFolder.delete();
outputFolder.mkdir();
outputFolder.deleteOnExit();

This vulnerability exists due to a race condition between the deletion of the randomly generated temporary file and the creation of the temporary directory.

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.

References

#8788

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: GHSA-pc22-3g76-gm6j

For more information

If you have any questions or comments about this advisory:

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CVE ID

CVE-2021-21428

Credits