Path Traversal in Rubyzip
CVE-2026-85396
rubyzip versions before 3.4.0 contain a path traversal vulnerability in Zip::Entry#extract that fails to properly validate extraction paths using prefix comparison without trailing separators. Attackers can craft archive entries with names like ../upload_backup/owned.sh to write files outside the intended extraction directory into sibling paths sharing the destination prefix.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.006 (45.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 45.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/geo-chen/oss/blob/main/rubyzip.md (technical-description)
- github.com/rubyzip/rubyzip (product)
- github.com/rubyzip/rubyzip/blob/v3.3.1/lib/zip/entry.rb (technical-description)
- github.com/rubyzip/rubyzip/commit/17edfbf4423b83211b075acc23a7d8640da63449 (patch)
- github.com/rubyzip/rubyzip/releases/tag/v3.4.0 (release-notes)
- www.vulncheck.com/advisories/rubyzip-before-3.4.0-path-traversal-in-zip-entry-e… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-85396?
- CVE-2026-85396 is a high-severity vulnerability in Rubyzip, classified under Path Traversal. CVSS score: 7.5/10. Published 2026-09-03.
- How severe is CVE-2026-85396?
- High severity. CVSS v3 base score is 7.5 out of 10.