Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
rubyzip versions before 3.4.0 are vulnerable to path traversal in Zip::Entry#extract, which checks extraction paths by prefix comparison without a trailing separator. An attacker who can supply a crafted zip archive can write files to sibling directories that share the destination's name prefix, outside the intended extraction directory. Upgrade to rubyzip 3.4.0 or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 8.7 | High | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N | CNA (VulnCheck) |
- CISA KEV Not listed.
- EPSS 0.0056, the 47th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:21 UTC First seen by agentprime
- 31 Oct 2026, 14:21 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-47m2-wp7j-p9vc
- OSV: GHSA-47m2-wp7j-p9vc
- nvd.nist.gov/vuln/detail/CVE-2026-85396
- github.com/rubyzip/rubyzip/commit/17edfbf4423b83211b075acc23a7d8640da63449
- github.com/geo-chen/oss/blob/main/rubyzip.md
- github.com/rubysec/ruby-advisory-db/blob/master/gems/rubyzip/CVE-2026-85396.yml
- github.com/rubyzip/rubyzip
- github.com/rubyzip/rubyzip/blob/v3.3.1/lib/zip/entry.rb
- github.com/rubyzip/rubyzip/releases/tag/v3.4.0
- www.vulncheck.com/advisories/rubyzip-before-3.4.0-path-traversal-in-zip-entry-extract-via-sibling-directory-prefix