CVE-2026-1527 undici is vulnerable to CRLF Injection via upgrade option
Attackers can inject CRLF sequences via the upgrade option to manipulate HTTP headers or smuggle data, affecting applications using undici.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-1527?
CVE-2026-1527 is a medium-severity vulnerability in Nodejs Undici, published on 12 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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` }
Weakness: CWE-93
Which versions are affected by CVE-2026-1527?
4 open source packages ship an affected version, including undici. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
undici npm | All versions | 6.24.0 |
undici npm | All versions | 6.24.0 |
undici npm | From 7.0.0 | 7.24.0 |
undici npm | From 7.0.0 | 7.24.0 |
Products include Nodejs Undici.
How do I fix CVE-2026-1527?
Upgrade undici to a fixed version for your release line: 6.24.0 or 7.24.0.
Is CVE-2026-1527 being exploited?
There is no known exploitation of CVE-2026-1527 in the wild and no public exploit code.
Other vulnerabilities in Nodejs Undici
- CVE-2026-109855 undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
- CVE-2026-109869 undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
- CVE-2026-87018 undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
- CVE-2026-19534 undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
- CVE-2026-12151 undici WebSocket client vulnerable to denial of service via fragment count bypass
Sources
Also known as BELL-CVE-2026-1527, CLEANSTART-2026-FZ57478, CLEANSTART-2026-WR15382, DEBIAN-CVE-2026-1527, ECHO-97b5-e152-578d, GHSA-4992-7rv2-5pvq and 12 more.