🛡️ CVE-2026-39245 — decompress

🟡 CVSS 6.2 — Medium ⚠️ Exploit Public CWE-22 NVD
6.2
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability none.

Weakness class

CVE-2026-39245 is classified as CWE-22: Path Traversal. A file path built from user input is not confined to the intended directory, letting an attacker reach files elsewhere on the filesystem.

Affected software

CVE-2026-39245 is recorded against 1 package.

  • decompress (fixed in 4.2.1)

Timeline and source

Published on 9 July 2026 and last revised on 13 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. Record sourced from NVD.

References

github.com
github.com
nvd.nist.gov
www.npmjs.com
github.com

Details

Severity MEDIUM
CVSS Score 6.2
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CWE CWE-22
Public Exploit ⚠️ Yes
Source NVD
Published 2026-07-09
Updated 2026-08-11
Modified 2026-07-13
Fix URL N/A

Affected Packages

Software From version Fixed in
decompress — 4.2.1

Exploit Protection

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CVE-2026-39245 carries CVSS 6.2 Medium rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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