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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 e

mediumCVSS 6.2CVE-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.

Details

Source
NVD Recent CVEs (US · database · site)
Severity
medium — CVSS 6.2
Published
2026-07-09
Last updated
2026-07-10
Exploitation
Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-39245

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-39245coverage & exploitation statusNVD · CVE.org

Recent advisories for decompress

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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