NuytsTech Security

CVE-2026-1527

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ImpactWhen an application passes user-controlled input to the upgrade option of client.request(), an attacker can inject CRLF sequences (rn) 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: upgradernupgrade: ${upgrade}rn`
}

More information : https://cna.openjsf.org/security-advisories.html

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