CVE-2026-84939: Apache FreeMarker, Apache FreeMarker: A malformed locale may be exploitable for path traversal attacks
Path traversal vulnerability in Apache FreeMarker template loading mechanism, if the attacker can specify an arbitrary malformed locale identifier to FreeMarker, and the localized lookup configuration setting is enabled (it's by default enabled).
This issue affects Apache FreeMarker from 2.2.0 through 2.3.34.
Users are recommended to upgrade to version 2.3.35. Disabling localized lookup in previous versions also mitigates this.
Note that even in versions affected by this vulnerability, the files that can be loaded remain restricted by the TemplateLoader that FreeMarker is configured to use. In particular, FileTemplateLoader prevents attempts to traverse outside the baseDir specified in its constructor. Other TemplateLoader implementations may allow access outside their designated base directory, but they are still constrained by the underlying storage mechanism—for example, a loader wrapping a Java class loader can only access resources that the class loader can load, while one wrapping a web application context can only access resources available through that context.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Apache FreeMarkerto a version that resolves this vulnerability.Fixed in 2.3.35 - Configuration
Disable localized lookup in FreeMarker to mitigate the path traversal condition when a malformed locale identifier is supplied (localized lookup is enabled by default in affected versions).
Apache FreeMarker localized lookup configuration = disabled
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Apache FreeMarker versions 2.2.0 through 2.3.34 are affected when localized lookup is enabled, which is the default. Exploitation also requires that an attacker can supply an arbitrary malformed locale identifier to FreeMarker.
Does the configured TemplateLoader affect the practical impact?
Yes. Files remain constrained by the configured TemplateLoader: FileTemplateLoader prevents traversal outside its configured baseDir. Other loaders may permit access beyond their designated base directory, but remain limited by their underlying storage, such as class-loader-accessible resources or resources available through a web application context.
What can be done before upgrading?
Upgrade to Apache FreeMarker 2.3.35. If an immediate upgrade is not possible, disabling localized lookup mitigates the issue in affected versions.