Summary
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.
Fix: Re-introduce BrutIO.sanitizePath() in ResFileDecoder.java before file write operations.
Impact
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-39973 has a CVSS score of 7.1 (High). The vector is requires local access, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.2); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-39973? CVE-2026-39973 is a high-severity path traversal vulnerability in org.apktool:apktool-lib (maven), affecting versions >= 3.0.0, < 3.0.2. It is fixed in 3.0.2. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-39973? CVE-2026-39973 has a CVSS score of 7.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.apktool:apktool-lib are affected by CVE-2026-39973? org.apktool:apktool-lib (maven) versions >= 3.0.0, < 3.0.2 is affected.
- Is there a fix for CVE-2026-39973? Yes. CVE-2026-39973 is fixed in 3.0.2. Upgrade to this version or later.
- Is CVE-2026-39973 exploitable, and should I be worried? Whether CVE-2026-39973 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-39973 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-39973? Upgrade
org.apktool:apktool-libto 3.0.2 or later.