Description

extract-zip through 2.0.1 containment-checks only the parent directory of each archive entry and never the entry's own final path component, so an archive containing two entries with identical names - a symlink whose target is outside the destination, followed by a regular file - writes through the planted symlink and yields an arbitrary file write outside the destination directory.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.1",
  "pubDate": "2026-08-17T14:20:20.737Z",
  "pubdate": "2026-08-17T14:20:20.737Z",
  "executiveSummary": "An arbitrary file write vulnerability exists in extract-zip through 2.0.1, allowing malicious archive payloads to write files outside of the intended destination directory. The vulnerability stems from insufficient containment checks that inspect only the parent directory of each archive entry rather than the entry's final path component.\nThis flaw enables an attacker with the ability to supply a maliciously crafted archive to achieve arbitrary file writes on systems utilizing vulnerable versions of the product. The risk implication is severe, as successful exploitation can lead to system compromise, arbitrary code execution, or sensitive data modification depending on the privileges of the process executing the extraction.\nExploitation requires the victim to process an untrusted archive containing specific sequences of entries. No special authentication or network exposure is inherently required beyond the mechanism used to ingest and extract the archive.",
  "technicalDetails": "The root cause of the vulnerability resides in the containment-check logic within the extraction routines of extract-zip through 2.0.1. Specifically, the validation mechanism checks only the parent directory of each archive entry for path traversal or containment violations, failing to evaluate the entry's own final path component.\nThis architectural oversight enables a race condition or sequential logic bypass during the extraction phase of specially crafted archive files. The attack flow involves an archive containing a specific sequence of at least two entries with identical names: first, a symbolic link whose target resolves to a location outside the intended destination directory, followed immediately by a regular file bearing the same name.\nWhen the vulnerable extraction routine processes the archive, it validates the parent directory containment for the symlink entry, which may pass depending on the relative path structure. The extractor then writes the symlink to the destination. Upon processing the subsequent regular file entry with the identical name, the extraction engine attempts to write the file payload.\nBecause the final path component is not adequately validated against the destination root and the path resolves through the previously planted symbolic link, the file write operation follows the symlink. Consequently, the payload is written to the arbitrary target location outside the intended destination directory, leading to an arbitrary file write condition.\nThe vulnerable component is the path validation and extraction handling logic in extract-zip across all versions through 2.0.1. Exploitation requires no authentication or network exposure, relying purely on the ingestion and extraction of a maliciously crafted archive payload by a local or remote process."
}