CVE-2026-1527
Undici has CRLF Injection in undici via `upgrade` option
Impact
### Impact When an application passes user-controlled input to the `upgrade` option of `client.request()`, an attacker can inject CRLF sequences (`\r\n`) to: 1. Inject arbitrary HTTP headers 2. 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: ```javascript // lib/dispatcher/client-h1.js:1121 if (upgrade) { header += `connection: upgrade\r\nupgrade: ${upgrade}\r\n` } ``` ### Patches Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later. ### Workarounds Sanitize the `upgrade` option string before passing to undici: ```javascript function sanitizeUpgrade(value) { if (/[\r\n]/.test(value)) { throw new Error('Invalid upgrade value') } return value } client.request({ upgrade: sanitizeUpgrade(userInput) }) ```
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | undici | < 6.24.0 | 6.24.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nodejs | Undici | before 6.24.0 from 7.0.0 before 7.24.0 |