CVE-2026-1527
Undici has CRLF Injection in undici via `upgrade` option
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` }
How to fix CVE-2026-1527
To remediate CVE-2026-1527, upgrade the affected package to a fixed version below.
- —no fix listed
- —upgrade to 6.24.0 or later
Is CVE-2026-1527 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0
- from 0, < 6.24.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM4.6 | CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N |