Summary
Junrar: LocalFolderExtractor mkdir escape allows directory creation outside extraction root
LocalFolderExtractor validates only the final canonical file path before extraction. However, makeFile() creates intermediate directories one path segment at a time without checking whether each created directory remains inside the destination folder.
A malicious RAR entry can make the final file path resolve inside the extraction destination, while causing intermediate mkdir() calls to create attacker-chosen directories outside the extraction root.
This is an extraction root escape via unchecked intermediate directory creation. The default impact is directory creation outside the intended destination, not unconditional arbitrary file content write.
Affected Code
src/main/java/com/github/junrar/LocalFolderExtractor.javacreateFile()checks only the final canonical path.makeFile()callsdir.mkdir()for each intermediate segment without containment checks.
Relevant code flow:
private File createFile(final FileHeader fh, final File destination) throws IOException {
String name = invariantSeparatorsPathString(fh.getFileName());
File f = new File(destination, name);
String dirCanonPath = f.getCanonicalPath();
if (!dirCanonPath.startsWith(destination.getCanonicalPath() + File.separator)) {
throw new IllegalStateException(...);
}
if (!f.exists()) {
f = makeFile(destination, name);
}
return f;
}
private File makeFile(final File destination, final String name) throws IOException {
final String[] dirs = name.split("/");
String path = "";
for (int i = 0; i < dirs.length - 1; i++) {
path = path + File.separator + dirs[i];
File dir = new File(destination, path);
dir.mkdir();
}
path = path + File.separator + dirs[dirs.length - 1];
final File f = new File(destination, path);
f.createNewFile();
return f;
}
Impact
An attacker who can supply a malicious RAR archive can create directories outside the intended extraction directory.
This violates the expected extraction boundary and can be used for filesystem pollution or file-vs-directory squatting. For example, an attacker can create a directory at a path where a later security-sensitive file is expected, causing future writes to that path to fail.
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-2026-86071 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. 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 (7.6.1); 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.
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Frequently Asked Questions
- What is CVE-2026-86071? CVE-2026-86071 is a low-severity path traversal vulnerability in com.github.junrar:junrar (maven), affecting versions <= 7.6.0. It is fixed in 7.6.1. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-86071? CVE-2026-86071 has a CVSS score of 3.7 (Low). 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 com.github.junrar:junrar are affected by CVE-2026-86071? com.github.junrar:junrar (maven) versions <= 7.6.0 is affected.
- Is there a fix for CVE-2026-86071? Yes. CVE-2026-86071 is fixed in 7.6.1. Upgrade to this version or later.
- Is CVE-2026-86071 exploitable, and should I be worried? Whether CVE-2026-86071 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-2026-86071 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-2026-86071? Upgrade
com.github.junrar:junrarto 7.6.1 or later.