CVE-2021-3856

Name: CVE-2021-3856
Creator: NVD / NIST
Published: 2022-08-26T16:15:09.57+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.86%

Last modified Jun 17, 2026

CVE-2021-3856 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. 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.. EPSS estimates a 0.86% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS Probability

0.86%

54.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Redhat	Keycloak	< 15.1.0

References

https://access.redhat.com/security/cve/CVE-2021-3856Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2010164Issue Tracking, Vendor Advisory
https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743Patch, Third Party Advisory
https://github.com/keycloak/keycloak/pull/8588Patch, Third Party Advisory
https://issues.redhat.com/browse/KEYCLOAK-19422Permissions Required, Vendor Advisory
https://access.redhat.com/security/cve/CVE-2021-3856Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2010164Issue Tracking, Vendor Advisory
https://github.com/keycloak/keycloak/commit/73f0474008e1bebd0733e62a22aceda9e5de6743Patch, Third Party Advisory
https://github.com/keycloak/keycloak/pull/8588Patch, Third Party Advisory
https://issues.redhat.com/browse/KEYCLOAK-19422Permissions Required, Vendor Advisory

Timeline

Published: Aug 26, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3856?

How severe is CVE-2021-3856?

CVE-2021-3856 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.86% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3856?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-3856?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST