GHSA-9j94-67jr-4cqj
MEDIUMRack session gets restored after deletion
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
rack-sessionReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
When using the Rack::Session::Pool middleware, simultaneous rack requests can restore a deleted rack session, which allows the unauthenticated user to occupy that session.
Details
Rack session middleware prepares the session at the beginning of request, then saves is back to the store with possible changes applied by host rack application. This way the session becomes to be a subject of race conditions in general sense over concurrent rack requests.
Impact
When using the Rack::Session::Pool middleware, and provided the attacker can acquire a session cookie (already a major issue), the session may be restored if the attacker can trigger a long running request (within that same session) adjacent to the user logging out, in order to retain illicit access even after a user has attempted to logout.
Mitigation
- Update to the latest version of
rack-session, or - Ensure your application invalidates sessions atomically by marking them as logged out e.g., using a
logged_outflag, instead of deleting them, and check this flag on every request to prevent reuse, or - Implement a custom session store that tracks session invalidation timestamps and refuses to accept session data if the session was invalidated after the request began.
Related
This code was previously part of rack in Rack < 3, see https://github.com/rack/rack/security/advisories/GHSA-vpfw-47h7-xj4g for the equivalent advisory in rack (affecting Rack < 3 only).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rack-session | ≥ 2.0.0&&< 2.1.1 | 2.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack-session. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update rack-session to 2.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9j94-67jr-4cqj is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-9j94-67jr-4cqj is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-9j94-67jr-4cqj. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-9j94-67jr-4cqj in your dependencies?
O3 detects GHSA-9j94-67jr-4cqj across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.