CVE-2023-23936
MEDIUMCVE-2023-23936 is a medium-severity (CVSS 6.5) CWE-93 vulnerability in undici. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2023-23936 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
CRLF Injection in Nodejs ‘undici’ via host
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
undicinpmDescription
Undici is an HTTP/1.1 client for Node.js. Starting with version 2.0.0 and prior to version 5.19.1, the undici library does not protect host HTTP header from CRLF injection vulnerabilities. This issue is patched in Undici v5.19.1. As a workaround, sanitize the headers.host string before passing to undici.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | ≥ 2.0.0&&< 5.19.1 | 5.19.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for undici. 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 undici to 5.19.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-23936 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-2023-23936 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-2023-23936. 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-2023-23936 in your dependencies?
O3 detects CVE-2023-23936 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.