Advisory details:
github_osv / GHSA-89m4-43j5-vhhx
| Advisory ID | github_osv/GHSA-89m4-43j5-vhhx |
| Aliases |
CVE-2026-86071
|
| Summary | Junrar: LocalFolderExtractor mkdir escape allows directory creation outside extraction root ## Summary `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.java` - `createFile()` checks only the final canonical path. - `makeFile()` calls `dir.mkdir()` for each intermediate segment without containment checks. Relevant code flow: ```java 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. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 3.3 |
| Risk | 1.6 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 3.7 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-89m4-43j5-vhhx/GHSA-89m4-43j5-vhhx.json |
| generic_textual | LOW |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/junrar/junrar | ||
| CVE-2026-86071 | https://nvd.nist.gov/vuln/detail/CVE-2026-86071 | |
| e6e333b195a1e3ad271a18fd79d8ac1eb5289343 | Other | https://github.com/junrar/junrar/commit/e6e333b195a1e3ad271a18fd79d8ac1eb5289343 |
| GHSA-89m4-43j5-vhhx | Other | https://github.com/junrar/junrar/security/advisories/GHSA-89m4-43j5-vhhx |
| v7.6.1 | Other | https://github.com/junrar/junrar/releases/tag/v7.6.1 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.