ZDF
Sign inSign up

Vulnerabilities

Vulnerability · CVE-2021-3856

ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader.

Published Aug 26, 2022 · catalog updated Jun 17, 2026 · ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2021-3856. EPSS is 1.16%. Act only if a listed version of ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium4.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.16%
Remediation
Version ranges on file
Affected products
cpe redhat/keycloak

ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe redhat/keycloak< 15.1.0

How to fix CVE-2021-3856

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-3856. EPSS is 1.16%. Act only if a listed version of ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows is installed.

Which versions are affected?

Compare what you have installed with < 15.1.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-22: Path Traversal; CWE-552: Files or Directories Accessible to External Parties. EPSS 1.16%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Keycloak security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 26, 2022 · Monitored products — high

    Detected

    ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.

  2. Jun 17, 2026 · Monitored products — high

    Updated

    ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.

Sources

  • CVE.orgVulnerability recordCVE-2021-3856

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2021-3856

    ClassLoaderTheme and ClasspathThemeResourceProviderFactory allows reading any file available as a resource to the classloader. By sending requests for theme resources with a relative path from an external HTTP client, the client will receive the content of random files if available.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • Monitored products — highNov 3, 2026