# CVE-2026-1528: undici is vulnerable to Malicious WebSocket 64-bit length overflows undici parser and crashes the client

> A malicious server can crash the undici client by sending a WebSocket frame with an excessively large 64-bit length, causing an integer overflow and fatal error.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Mar 2026
- **Updated:** 14 Sep 2026
- **Also known as:** BELL-CVE-2026-1528, CLEANSTART-2026-TJ00252, CLEANSTART-2026-ZX81460, DEBIAN-CVE-2026-1528, ECHO-a34f-8d81-b926, GHSA-f269-vfmq-vjvj, MINI-2667-43w7-4jc8, MINI-67qw-chp4-mj8f, MINI-9fx9-vvwr-97gj, MINI-9wc3-xrm4-5rfc, MINI-fxgq-f6hg-wv5c, MINI-gm9m-q896-grpm, MINI-hgg9-9wr6-7hwv, MINI-rxpj-x747-w6p2, MINI-w7v3-vfrh-fx5j, MINI-xm69-ph56-57vp, ROOT-APP-NPM-CVE-2026-1528, UBUNTU-CVE-2026-1528

## What is CVE-2026-1528?

CVE-2026-1528 is a high-severity vulnerability in Nodejs Undici, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

ImpactA server can reply with a WebSocket frame using the 64-bit length form and an extremely large length. undici's ByteParser overflows internal math, ends up in an invalid state, and throws a fatal TypeError that terminates the process.

Patches

Patched in the undici version v7.24.0 and v6.24.0. Users should upgrade to this version or later.

Weakness: CWE-248 (Uncaught Exception), CWE-1284 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-1528?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `undici` | npm | From 6.0.0 | 6.24.0 |
| `undici` | npm | From 6.0.0 | 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-2026-1528?

Upgrade undici to a fixed version for your release line: 6.24.0 or 7.24.0.

## Is CVE-2026-1528 being exploited?

There is no known exploitation of CVE-2026-1528 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-2026-1528 and fix it if it is affected.

What it is: CVE-2026-1528 is a high-severity vulnerability in Nodejs Undici, published on 12 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-1528 in the wild and no public exploit code.

Affected packages and fixed versions:
- undici (npm): affected from 6.0.0; fixed in 6.24.0
- undici (npm): affected from 6.0.0; 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-2026-1528/ (Markdown: https://insights.sbomify.com/CVE-2026-1528/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1528
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1528
- OSV: https://osv.dev/vulnerability/CVE-2026-1528

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1528/
Summaries are generated and may contain mistakes; the official description above is the record.