CVE-2025-23167: 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.

CSIRTS triage

What: HTTP/1 parser accepts malformed header termination (`\r\n\rX` instead of `\r\n\r\n`), enabling HTTP request smuggling.
Who is affected: Node.js 20 applications acting as HTTP servers or proxies, especially behind other proxies.
Urgency: Medium priority; request smuggling bypasses proxy controls; active attack surface.
Action: Update Node.js 20 to patched version with strict HTTP header termination validation.

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EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2025-231670.51% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 41% of all EPSS-scored CVEs.

CVE	CSIRTS overview	External
CVE-2025-23167	coverage & exploitation status	NVD · CVE.org

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