CVE-2026-39973
Description
Apktool is a tool for reverse engineering Android APK files. In versions 3.0.0 and 3.0.1, a path traversal vulnerability in `brut/androlib/res/decoder/ResFileDecoder.java` allows a maliciously crafted APK to write arbitrary files to the filesystem during standard decoding (`apktool d`). This is a security regression introduced in commit e10a045 (PR #4041, December 12, 2025), which removed the `BrutIO.sanitizePath()` call that previously prevented path traversal in resource file output paths. An attacker can embed `../` sequences in the `resources.arsc` Type String Pool to escape the output directory and write files to arbitrary locations, including `~/.ssh/config`, `~/.bashrc`, or Windows Startup folders, escalating to RCE. The fix in version 3.0.2 re-introduces `BrutIO.sanitizePath()` in `ResFileDecoder.java` before file write operations.
How to fix
- apktool apktool3.0.2 or later
- org.apktool:apktool-lib3.0.2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| apktool apktool | 3.0.0 ≤ v < 3.0.2 | 3.0.2 |
| org.apktool:apktool-libMaven | 3.0.0 ≤ v < 3.0.2 | 3.0.2 |
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