CVE-2026-84939: Apache FreeMarker: A malformed locale may be exploitable for path traversal attacks

[Dániel Dékány <ddekany () apache org>]

Affected versions:

- Apache FreeMarker (org.freemarker:freemarker) 2.2.0 through 2.3.34
- Apache FreeMarker (org.freemarker:freemarker) 2.3.35 unaffected
- Apache FreeMarker (org.freemarker:freemarker-gae) 2.2.0 through 2.3.34
- Apache FreeMarker (org.freemarker:freemarker-gae) 2.3.35 unaffected

Description:

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.

References:

https://freemarker.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-84939