Vulnerability · Published Jul 9, 2026 · Assigned by mitre
CVE-2026-39245
Medium 6.2
In plain English
A medium-severity path traversal in the affected software. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities).
Official 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.
Affected products (as reported)
Weakness: CWE-22 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N