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`
}
* 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`
}
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Fixes
Solution
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Workaround
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References
History
Fri, 13 Mar 2026 00:15:00 +0000
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threat_severity
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threat_severity
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Thu, 12 Mar 2026 20:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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` } | |
| Title | undici is vulnerable to CRLF Injection via upgrade option | |
| Weaknesses | CWE-93 | |
| References |
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| Metrics |
cvssV3_1
|
Projects
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Status: PUBLISHED
Assigner: openjs
Published:
Updated: 2026-03-12T20:17:18.984Z
Reserved: 2026-01-28T12:05:08.491Z
Link: CVE-2026-1527
No data.
Status : Received
Published: 2026-03-12T21:16:25.137
Modified: 2026-03-12T21:16:25.137
Link: CVE-2026-1527
OpenCVE Enrichment
No data.
Weaknesses