CVE-2026-1527: Node.js Undici

Medium severity, CVSS 4.6. EPSS: 0.3% chance of exploitation in the next 30 days.

ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (\r\n) to: * Inject arbitrary HTTP headers * Terminate the HTTP request prematurely and smuggle raw data to non-HTTP services (Redis, Memcached, Elasticsearch) The vulnerability exists because undici writes the upgrade value directly to the socket without validating for invalid header characters: // lib/dispatcher/client-h1.js:1121 if (upgrade) { header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n` }

Affected products

• Node.js Undici: before 6.24.0 (fixed in 6.24.0); from 7.0.0, before 7.24.0 (fixed in 7.24.0)

Published 2026-03-12. Last modified 2026-06-17.