What’s Vulnerable › Vulnerabilities

CVE-2021-3856

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2022-08-26 · updated 2026-06-17
• Weakness: CWE-552

Description

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.

Affected products

• Keycloak: before 15.1.0 — fixed in 15.1.0

How to fix

Upgrade to a fixed version: Keycloak 15.1.0. Check the vendor advisory for mitigations.

References

• https://access.redhat.com/security/cve/CVE-2021-3856
• https://bugzilla.redhat.com/show_bug.cgi?id=2010164
• https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743
• https://github.com/keycloak/keycloak/pull/8588
• https://issues.redhat.com/browse/KEYCLOAK-19422
• https://access.redhat.com/security/cve/CVE-2021-3856
• https://bugzilla.redhat.com/show_bug.cgi?id=2010164
• https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743
• https://github.com/keycloak/keycloak/pull/8588
• https://issues.redhat.com/browse/KEYCLOAK-19422

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