CVE-2026-84939
Description
A flaw was found in Apache FreeMarker. A remote attacker could exploit a path traversal vulnerability in the template loading mechanism by providing a specially crafted, malformed locale identifier. This is possible if the localized lookup configuration setting is enabled, which is the default. This vulnerability could allow an attacker to access files outside the intended base directory, potentially leading to information disclosure or unauthorized file access, depending on the configured TemplateLoader.
Statement
This is an Important path traversal vulnerability in Apache FreeMarker, affecting Red Hat JBoss Fuse, Red Hat Build of Keycloak, and Red Hat Single Sign-On. An attacker can exploit this flaw by providing a malformed locale identifier when localized lookup is enabled by default, potentially accessing restricted files. While FileTemplateLoader limits traversal to its base directory, other TemplateLoader implementations may allow broader access, justifying the Important impact.
Mitigation
To mitigate this vulnerability, disable the localized lookup configuration setting within your Apache FreeMarker deployment. This setting is enabled by default and its deactivation prevents the processing of malformed locale identifiers that could lead to path traversal. Consult your application's documentation for specific instructions on how to configure FreeMarker to disable localized lookup. A restart of the affected application or service will be required for the changes to take effect. Disabling localized lookup may impact applications that rely on this feature for internationalization.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | None | N/A | High |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
The attacker may be able to create or overwrite critical files that are used to execute code, such as programs or libraries.
Integrity
Technical Impact: Modify Files or Directories
The attacker may be able to overwrite or create critical files, such as programs, libraries, or important data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, appending a new account at the end of a password file may allow an attacker to bypass authentication.
Confidentiality
Technical Impact: Read Files or Directories
The attacker may be able read the contents of unexpected files and expose sensitive data. If the targeted file is used for a security mechanism, then the attacker may be able to bypass that mechanism. For example, by reading a password file, the attacker could conduct brute force password guessing attacks in order to break into an account on the system.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
The attacker may be able to overwrite, delete, or corrupt unexpected critical files such as programs, libraries, or important data. This may prevent the product from working at all and in the case of protection mechanisms such as authentication, it has the potential to lock out product users.
Frequently Asked Questions
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