IzPack is a widely used tool for packaging applications on the Java platform as cross-platform installers. In 5.2.6 and earlier, UnpackerBase.unpack() in izpack-installer/src/main/java/com/izforge/izpack/installer/unpacker/UnpackerBase.java obtains an attacker-controlled PackFile targetPath, passes it through IoHelper.translatePath(), which only converts separators, and constructs a File without normalizing parent-directory segments or enforcing destination containment. A malicious installer pack entry containing ../ sequences can therefore write outside the intended installation directory to startup folders, executable search paths, or other locations accessible with the victim's privileges when the victim runs the installer.

IzPack versions 5.2.6 and earlier contain a path traversal vulnerability in the UnpackerBase.unpack() method. The vulnerability arises because attacker-controlled PackFile targetPath values are passed through IoHelper.translatePath(), which only converts path separators without normalizing parent-directory segments or enforcing destination containment. This allows a malicious installer pack entry containing ../ sequences to write files outside the intended installation directory. Exploitation could result in files being written to startup folders, executable search paths, or other sensitive locations accessible with the victim's privileges. The attack is triggered when a victim runs a maliciously crafted installer. Fixes have been committed to the IzPack GitHub repository and a security advisory has been published. Users are advised to update to a patched version as soon as available.