CVE-2021-21363 is a high-severity (CVSS 7) CWE-378 vulnerability in io.swagger:swagger-codegen. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-21363 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Generator Web Application: Local Privilege Escalation Vulnerability via System Temp Directory
Real-World Exposure
io.swagger:swagger-codegenReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.swagger:swagger-codegen | all versions | 2.4.19 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.swagger:swagger-codegen. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update io.swagger:swagger-codegen to 2.4.19 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21363 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-21363 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-21363. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-21363 in your dependencies?
O3 detects CVE-2021-21363 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.