How severe is CVE-2021-21364?

CVE-2021-21364 has a CVSS score of 5.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-21364?

CVE-2021-21364 affects the following packages: io.swagger:swagger-codegen (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-21364?

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-2021-21364 is resolved across your whole dependency graph.

How do I detect CVE-2021-21364 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.swagger:swagger-codegen, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-21364 if there is no patch (or I can't update yet)?

Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Is CVE-2021-21364 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21364 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-21364?

CVE-2021-21364 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 19th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-21364?

CVE-2021-21364 is classified as Information Exposure (CWE-200), CWE-378 (CWE-378), CWE-732 (CWE-732). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-21364 published, and has it been updated?

CVE-2021-21364 was published on March 11, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2021-21364 — swagger-codegen

MEDIUMFix: swagger-api/swagger-codegen@35adbd5

CVE-2021-21364 is a medium-severity (CVSS 5.5) Information Exposure vulnerability in io.swagger:swagger-codegen. A fix is available for io.swagger:swagger-codegen — see the affected versions and patch details below.

Generated Code Contains Local Information Disclosure Vulnerability

Also known asGHSA-hpv8-9rq5-hq7w

Published

Mar 11, 2021

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 12, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs19th percentile — riskier than 19% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-21364 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

☕io.swagger:swagger-codegen

Real-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

Impact

This vulnerability impacts generated code. If this code was generated as a one-off occasion, not as a part of an automated CI/CD process, this code will remain vulnerable until fixed manually!

On Unix-Like systems, the system temporary directory is shared between all local users. When files/directories are created, the default umask settings for the process are respected. As a result, by default, most processes/apis will create files/directories with the permissions -rw-r--r-- and drwxr-xr-x respectively, unless an API that explicitly sets safe file permissions is used.

Java Code

The method File.createTempFile from the JDK is vulnerable to this local information disclosure vulnerability.

Patches

Fix has been applied to the master branch with:

https://github.com/swagger-api/swagger-codegen/commit/35adbd552d5f99b3ff1e0e59da228becc85190f2

included in release: 2.4.19

Workarounds

Users can remediate the vulnerability in non patched version by manually (or programmatically e.g. in CI) updating the generated source code to use java.nio.files.Files temporary file creation instead of java.io.File, e.g. by changing


    if (tempFolderPath == null)
      return File.createTempFile(prefix, suffix);
    else
      return File.createTempFile(prefix, suffix, new File(tempFolderPath));


    if (tempFolderPath == null)
      return Files.createTempFile(prefix, suffix).toFile();
    else
      return Files.createTempFile(Paths.get(tempFolderPath), prefix, suffix).toFile();

or generally changing:


File.createTempFile(prefix, suffix);


Files.createTempFile(prefix, suffix).toFile();

References

For more information

If you have any questions or comments about this advisory:

Email us at [email protected]

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 code exists in the code generator, in the generated code.

In this case, I believe this is only a local information disclosure. IE. another user can read the information, not replace it.

In particular, the method File.createTempFile from the JDK is vulnerable to this local information disclosure vulnerability.

This is because File.createTempFile creates a file inside of the system temporary directory with the permissions: -rw-r--r--. Thus the contents of this file are viewable by all other users locally on the system.

https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-codegen/src/main/resources/kotlin-client/infrastructure/ApiClient.kt.mustache#L209

https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-codegen/src/main/resources/finch/api.mustache#L84

https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-codegen/src/main/resources/Java/libraries/okhttp-gson/ApiClient.mustache#L831-L834

https://github.com/swagger-api/swagger-codegen/blob/068b1ebcb7b04a48ad38f1cadd24bb3810c9f1ab/modules/swagger-codegen/src/main/resources/Java/libraries/jersey2/ApiClient.mustache#L630-L633

The fix here is to switch to the Files API, instead of File as that appropriately sets the file permissions.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.swagger:swagger-codegen`	all versions	2.4.19`io.swagger:swagger-codegen:2.4.19`

Affected Products

1 product · 1 configurations

Application

swagger-codegensmartbear

< 2.4.19

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.swagger:swagger-codegen, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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-2021-21364 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Frequently Asked Questions

### Impact **This vulnerability impacts generated code.** If this code was generated as a one-off occasion, not as a part of an automated CI/CD process, this code will remain vulnerable until fixed manually! On Unix-Like systems, the system temporary directory is shared between all local users. When files/directories are created, the default `umask` settings for the process are respected. As a result, by default, most processes/apis will create files/directories with the permissions `-rw-r--r--` and `drwxr-xr-x` respectively, unless an API that explicitly sets safe file permissions is used.