CVE-2025-23167
Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n` vulnerability
Node.js · A flaw in Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n`. This inconsistency enables request smuggling, allowing attackers to bypass proxy-based access controls and submit unauthorized requests. The issue was resolved by upgrading `llhttp` to version 9, which enforces correct header termination. Impact: * This vulnerability affects only Node.js 20.x users prior to the `llhttp` v9 upgrade.
MSRC advisory May 31, 2026
Alert details
- Source feed
- Microsoft MSRC
- CVE ID
- CVE-2025-23167
- CWE
- CWE-444
- Affected products
- A flaw in Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n`. This inconsistency enables request smuggling, allowing attackers to bypass proxy-based access controls and submit unauthorized requests. The issue was resolved by upgrading `llhttp` to version 9, which enforces correct header termination. Impact: * This vulnerability affects only Node.js 20.x users prior to the `llhttp` v9 upgrade. · A A flaw in Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n`. This inconsistency enables request smuggling, allowing attackers to bypass proxy-based access controls and submit unauthorized requests. The issue was resolved by upgrading `llhttp` to version 9, which enforces correct header termination. Impact: * This vulnerability affects only Node.js 20.x users prior to the `llhttp` v9 upgrade. · A
What happened
Information published.
What it means for your business
A A flaw in Node.js 20's HTTP parser allows improper termination of HTTP/1 headers using `\r\n\rX` instead of the required `\r\n\r\n`. This inconsistency enables request smuggling, allowing attackers to bypass proxy-based access controls and submit unauthorized requests. The issue was resolved by upgrading `llhttp` to version 9, which enforces correct header termination. Impact: * This vulnerability affects only Node.js 20.x users prior to the `llhttp` v9 upgrade. (CVE-2025-23167) was added to Microsoft’s security update guidance. Information published. PremierePC tracks MSRC advisories for Upstate SC businesses — patch or open a ticket if you need help verifying exposure.
CVSS score
6.5 (Medium)
EPSS probability
0.47%
Sources
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