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A vulnerability has been found in Keycloak (the affected version is unknown) and classified as problematic. This vulnerability affects the function ClassLoaderTheme/ClasspathThemeResourceProviderFactory. The manipulation with an unknown input leads to a path traversal vulnerability. The CWE definition for the vulnerability is CWE-23. The software uses external input to construct a pathname that should be within a restricted directory, but it does not properly neutralize sequences such as ".." that can resolve to a location that is outside of that directory. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The weakness was disclosed 08/26/2022. The advisory is available at This vulnerability was named CVE-2021-3856 since 10/04/2021. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1006 by the MITRE ATT&CK project.

Applying the patch 73f0474008e1bebd0733e62a22aceda9e5de6743 is able to eliminate this problem. The bugfix is ready for download at




  • free

CPE 2.3info

CPE 2.2info


VulDB Meta Base Score: 5.0
VulDB Meta Temp Score: 4.8

VulDB Base Score: 5.0
VulDB Temp Score: 4.8
VulDB Vector: 🔒
VulDB Reliability: 🔍



VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍


Class: Path traversal
CWE: CWE-23 / CWE-22
ATT&CK: T1006

Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒


Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍


Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 73f0474008e1bebd0733e62a22aceda9e5de6743


10/04/2021 CVE reserved
08/26/2022 +326 days Advisory disclosed
08/26/2022 +0 days VulDB entry created
10/02/2022 +37 days VulDB last update


Advisory: 73f0474008e1bebd0733e62a22aceda9e5de6743
Status: Confirmed

CVE: CVE-2021-3856 (🔒)


Created: 08/26/2022 08:37 PM
Updated: 10/02/2022 11:54 AM
Changes: 08/26/2022 08:37 PM (39), 10/02/2022 11:54 AM (1)
Complete: 🔍


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