Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Decompress Project | Decompress | <= 4.2.1 |
Related Weaknesses (CWE)
References
- https://github.com/kevva/decompressProduct
- https://github.com/kevva/decompress/issues/115ExploitVendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2020-12265US Government Resource
- https://www.npmjs.com/package/decompressProduct
- https://github.com/kevva/decompress/issues/115ExploitVendor Advisory
FAQ
What is CVE-2026-39245?
CVE-2026-39245 is a vulnerability with a CVSS score of 6.2 (MEDIUM). 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 valid...
How severe is CVE-2026-39245?
CVE-2026-39245 has been rated MEDIUM with a CVSS base score of 6.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-39245?
Check the references section above for vendor advisories and patch information. Affected products include: Decompress Project Decompress.