Answer in brief
CVE-2026-1527 records a Medium severity (CVSS 4.6) vulnerability in Undici has CRLF Injection in undici via `upgrade` option. The current sources do not mark it as known exploited. The current feed maps undici (npm), undici (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 4.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps undici (npm), undici (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| undicinpm | >=0 <6.24.0 | 6.24.0 |
| undicinpm | >=7.0.0 <7.24.0 | 7.24.0 |
Published upstream
Mar 13, 2026
Evidence: source:osv:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:recordFirst seen by HOL
Sep 10, 2026
### 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) }) ```
Quoted source text, attributed separately from HOL analysis.