GHSA-3h57-hmj3-gj3p
HIGHRack has possible DoS Vulnerability in Multipart MIME parsing
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💎rack💎rack💎rackReal-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
There is a possible DoS vulnerability in the Multipart MIME parsing code in Rack. This vulnerability has been assigned the CVE identifier CVE-2023-27530.
Versions Affected: All. Not affected: None Fixed Versions: 3.0.4.2, 2.2.6.3, 2.1.4.3, 2.0.9.3
Impact
The Multipart MIME parsing code in Rack limits the number of file parts, but does not limit the total number of parts that can be uploaded. Carefully crafted requests can abuse this and cause multipart parsing to take longer than expected.
All users running an affected release should either upgrade or use one of the workarounds immediately.
Workarounds
A proxy can be configured to limit the POST body size which will mitigate this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | rack | all versions | 2.0.9.3 |
| 💎RubyGems | rack | ≥ 2.1.0&&< 2.1.4.3 | 2.1.4.3 |
| 💎RubyGems | rack | ≥ 2.2.0&&< 2.2.6.3 | 2.2.6.3 |
| 💎RubyGems | rack | ≥ 3.0.0&&< 3.0.4.2 | 3.0.4.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for rack. 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 to 2.0.9.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3h57-hmj3-gj3p 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-3h57-hmj3-gj3p 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-3h57-hmj3-gj3p. 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-3h57-hmj3-gj3p in your dependencies?
O3 detects GHSA-3h57-hmj3-gj3p across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.