Creation of Temporary File in Directory with Insecure Permissions in the OpenAPI-Generator online generator

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.3 · CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

• CVE-2021-21428: 0.35% estimated exploitation activity in the next 30 days; percentile 28.85 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

11 May 2021, 00:04 UTC

Last modified by the source

30 Jun 2023, 20:30 UTC

Source last checked

26 Oct 2026, 16:11 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-23x4-m842-fmwf

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# Patch Next advisory brief: CVE-2021-21428

Advisory: Creation of Temporary File in Directory with Insecure Permissions in the OpenAPI-Generator online generator
IDs: CVE-2021-21428, GHSA-23x4-m842-fmwf
Record: https://patchnext.com/advisories/cve-2021-21428 (revision 1, source checked 26 Oct 2026, 16:11 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.openapitools:openapi-generator-online 5.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.openapitools:openapi-generator-online: affected < 5.1.0; fixed in 5.1.0

## Suggested inspection (read-only)
- Maven org.openapitools:openapi-generator-online: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.openapitools:openapi-generator-online.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-23x4-m842-fmwf (GitHub-reviewed advisory GHSA-23x4-m842-fmwf lists affected ranges: Maven org.openapitools:openapi-generator-online >=0 <5.1.0)

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