CVE-2023-40175 is a high-severity (CVSS 7.3) CWE-444 vulnerability in puma. O3 Security confirms whether CVE-2023-40175 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Inconsistent Interpretation of HTTP Requests in puma
Real-World Exposure
puma💎pumaReal-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
Puma is a Ruby/Rack web server built for parallelism. Prior to versions 6.3.1 and 5.6.7, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers in a way that allowed HTTP request smuggling. Severity of this issue is highly dependent on the nature of the web site using puma is. This could be caused by either incorrect parsing of trailing fields in chunked transfer encoding bodies or by parsing of blank/zero-length Content-Length headers. Both issues have been addressed and this vulnerability has been fixed in versions 6.3.1 and 5.6.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | puma | all versions | 5.6.7 |
| 💎RubyGems | puma | ≥ 6.0.0&&< 6.3.1 | 6.3.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for puma. 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 puma to 5.6.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40175 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 CVE-2023-40175 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 CVE-2023-40175. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-40175 in your dependencies?
O3 detects CVE-2023-40175 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.