# 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.

- **Severity:** Medium 4.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:N`)
- **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:** Yes
- **Published:** 12 Mar 2026
- **Updated:** 13 Mar 2026
- **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, MINI-3fgx-hccc-hm6q, MINI-4rgr-2f52-j36h, MINI-fcfc-f83v-fq5c, MINI-g4mv-4p5v-f7mp, MINI-h444-fq94-jfc2, MINI-h5xc-966m-ccr9, MINI-j5pw-7gjw-738g, MINI-m554-ppx8-r58x, MINI-phmp-vjcv-cqrx, MINI-pmg3-6ch3-v3f3, ROOT-APP-NPM-CVE-2026-1527, UBUNTU-CVE-2026-1527

## 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 (Improper Neutralization of CRLF Sequences)

## Which versions are affected by CVE-2026-1527?

4 open source packages ship an affected version, including undici. It affects 1 product.


| Package | Ecosystem | 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: 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](https://insights.sbomify.com/CVE-2026-109855/): undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake (high 7.5)
- [CVE-2026-109869](https://insights.sbomify.com/CVE-2026-109869/): undici vulnerable to Denial of Service via unhandled error on excessive content-encodings (high 7.5)
- [CVE-2026-87018](https://insights.sbomify.com/CVE-2026-87018/): undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation (high 7.5)
- [CVE-2026-19534](https://insights.sbomify.com/CVE-2026-19534/): undici vulnerable to Denial of Service via unrequested WebSocket subprotocol (high 7.5)
- [CVE-2026-12151](https://insights.sbomify.com/CVE-2026-12151/): undici WebSocket client vulnerable to denial of service via fragment count bypass (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1527 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-1527 in the wild and no public exploit code.

Affected packages and fixed versions:
- undici (npm): affected all versions; fixed in 6.24.0
- undici (npm): affected all versions; fixed in 6.24.0
- undici (npm): affected from 7.0.0; fixed in 7.24.0
- undici (npm): affected from 7.0.0; fixed in 7.24.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-1527/ (Markdown: https://insights.sbomify.com/CVE-2026-1527/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1527
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1527
- OSV: https://osv.dev/vulnerability/CVE-2026-1527

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1527/
Summaries are generated and may contain mistakes; the official description above is the record.