CVE-2023-23936 is a medium-severity (CVSS 6.5) CWE-93 vulnerability in undici. 1 public exploit or proof-of-concept reference is indexed, 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
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
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
Impact
undici library does not protect host HTTP header from CRLF injection vulnerabilities.
Patches
This issue was patched in Undici v5.19.1.
Workarounds
Sanitize the headers.host string before passing to undici.
References
Reported at https://hackerone.com/reports/1820955.
Credits
Thank you to Zhipeng Zhang (@timon8) for reporting this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | undici | ≥ 2.0.0&&< 5.19.1 | 5.19.1npm install undici@5.19.1 |
Affected Products
node.jsnodejsundicinodejsResearch 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.
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?
Find it across npm, including transitive dependencies.