CVE-2026-39245: decompress_project decompress

Vulnerability summary

CVE-2026-39245 is a medium (CVSS 6.2) vulnerability in decompress_project decompress. EPSS estimates a 0.38% chance of exploitation in the next 30 days, higher than 31.5% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 09-07-2026
   PublishedVulnerability first disclosed.
2. 10-07-2026
   Last modifiedVulnerability information updated.

Description

decompress before 4.2.2 contains an improper path containment check that enables directory traversal and arbitrary file write. The safeMakeDir function (index.js line 29) and the extraction path validation (index.js line 106) use String.indexOf() to verify the resolved path is within the output directory: realDestinationDir.indexOf(realOutputPath) !== 0. This check is flawed because it does not enforce a path separator boundary. For example, "/tmp/app_config".indexOf("/tmp/app") returns 0, incorrectly passing the check even though /tmp/app_config is outside /tmp/app. Combined with the unvalidated symlink creation in the same package, an attacker can write arbitrary files to directories adjacent to the extraction target. This is a bypass of the fix for CVE-2020-12265. The correct check requires appending a path separator: realParentPath.indexOf(realOutputPath + path.sep) !== 0.

• CWE-22Improper Limitation of a Pathname to a Restricted DirectoryThe product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.