Path Traversal in Decompress Project
CVE-2026-39245
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (29.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/kevva/decompress (Product)
- www.npmjs.com/package/decompress (Product)
- nvd.nist.gov/vuln/detail/CVE-2020-12265 (US Government Resource)
- github.com/kevva/decompress/issues/115 (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-39245?
- CVE-2026-39245 is a medium-severity vulnerability in Decompress Project, classified under Path Traversal. CVSS score: 6.2/10. Published 2026-07-09.
- How severe is CVE-2026-39245?
- Medium severity. CVSS v3 base score is 6.2 out of 10.