CVE-2023-23936 is a medium-severity (CVSS 6.5) CWE-93 vulnerability in undici. 1 public exploit reference exists, so weaponization risk is real. A fix is available for undici — see the affected versions and patch details below.
CRLF Injection in Nodejs ‘undici’ via host
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-23936.
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.
How urgent is this, really
CVE-2023-23936 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
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 | 5.19.1npm install undici@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-23936 can be triaged on real exposure rather than presence alone.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 8 | nodejs:16-8070020230314140722.bd1311ed | RHSA-2023:1582 |
| Red Hat Enterprise Linux 8 | nodejs:18-8070020230322080930.bd1311ed | RHSA-2023:1583 |
| Red Hat Enterprise Linux 9 | nodejs:18-9020020230327152102.rhel9 | RHSA-2023:2654 |
| Red Hat Enterprise Linux 9 | nodejs-1:16.19.1-1.el9_2 | RHSA-2023:2655 |
| Red Hat Enterprise Linux 9.0 Extended Update Support | nodejs-1:16.20.2-1.el9_0 | RHSA-2023:5533 |
Frequently Asked Questions
Is CVE-2023-23936 in your dependencies?
O3 Security finds CVE-2023-23936 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.