CVE intelligence and bounded remediation

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`

Medium CVSS 6.5

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.

Severity
Medium
CVSS
6.5 (3.0)
Published
2025-05-19
CISA KEV
Not currently listed
Ecosystem
javascript/npm
Weaknesses
CWE-444

Affected products

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Matched remediation archetype

HTTP request smuggling and message-boundary ambiguity

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Check exposure

  • Inventory every proxy, CDN, gateway, load balancer, service mesh, and application server hop on affected request paths.
  • Compare documented parsing and normalization behavior for message length, transfer coding, duplicate headers, and protocol translation.
  • Identify connection reuse and which downstream services trust headers added by intermediaries.

Remediate safely

  • Update affected intermediaries and origin servers and align them on a single standards-compliant request framing policy.
  • Reject ambiguous length, transfer-coding, duplicate, malformed, and unsupported framing before forwarding.
  • Normalize or remove hop-by-hop and identity headers at one controlled boundary and add multi-hop regression tests.

Authoritative sources

Complete CVE record and remediation plan

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