# CVE-2026-85396: rubyzip path traversal in Entry#extract

Source: https://junglewise.ai/threats/cve-2026-85396-rubyzip-path-traversal-in-entry-extract  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-03. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-85396 · Severity: high · CVSS 7.5 · Published 2026-09-03

rubyzip is a popular Ruby library for creating and extracting ZIP archive files. Versions before 3.4.0 contain a path traversal vulnerability that allows attackers to extract files outside the intended directory. When processing a specially crafted ZIP archive, files can be written to sibling directories, potentially overwriting sensitive files and compromising systems that extract untrusted archives.

Technologies: [rubyzip (RubyGems)](https://junglewise.ai/threats/technologies/rubygems-rubyzip). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-85396 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85396 being exploited in the wild.

**How severe is CVE-2026-85396?** High severity, with a CVSS score of 7.5, published 3 September 2026.

**Which products and versions are affected?** rubyzip (RubyGems) ECOSYSTEM:introduced=0,fixed=3.4.0.

**Is there a fix for CVE-2026-85396?** Yes. rubyzip (RubyGems): upgrade to 3.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-85396 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-85396?** Check whether you run rubyzip (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- rubyzip (RubyGems): upgrade to 3.4.0 or later

  ```sh
  bundle update rubyzip
  ```


## Technical details

The vulnerability is a path traversal flaw in the Entry#extract method (lib/zip/entry.rb lines 289–303) that uses a simple string prefix check without a trailing separator to validate extraction paths. An attacker can craft a ZIP entry with a name like ../upload_backup/owned.sh; when extracting to a destination like /tmp/rzv/upload, the vulnerable code accepts /tmp/rzv/upload_backup/owned.sh because it starts with the prefix /tmp/rzv/upload. The flaw exists because the check does not require an exact match or a trailing directory separator. No authentication is required; the vulnerability is triggered whenever an application extracts a malicious ZIP archive. An attacker can write arbitrary files to sibling directories of the extraction target. The fix, available in version 3.4.0, requires either an exact path match or a trailing separator in the prefix check.

## Affected products

- rubyzip rubyzip before 3.4.0

## Identifiers

- CVE-2026-85396
- GHSA-47m2-wp7j-p9vc

## Timeline

- 2026-06-04: disclosed
- 2026-09-03: patched

## References

- [https://github.com/geo-chen/oss/blob/main/rubyzip.md](https://github.com/geo-chen/oss/blob/main/rubyzip.md)
- [https://github.com/rubyzip/rubyzip](https://github.com/rubyzip/rubyzip)

## Related threats

- [Rubyzip denial of service](https://junglewise.ai/threats/cve-2019-16892-rubyzip-denial-of-service)
- [Rubyzip gem contains a Directory Traversal vulnerability in zip file component](https://junglewise.ai/threats/cve-2018-1000544-rubyzip-gem-contains-a-directory-traversal-vulnerability-in-zip)
- [High severity vulnerability that affects rubyzip](https://junglewise.ai/threats/high-severity-vulnerability-that-affects-rubyzip-e963e623)
- [Directory traversal vulnerability in RubyZip](https://junglewise.ai/threats/cve-2017-5946-directory-traversal-vulnerability-in-rubyzip)