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Vulnerability DatabaseCVE-2026-1527
CVE-2026-1527:
JavaScript vulnerability analysis and mitigation
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
}
Source: NVD
Related JavaScript vulnerabilities:
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