Skip to content

Undici: Malicious WebSocket 64-bit length overflows parser and crashes the client

High severity GitHub Reviewed Published Mar 12, 2026 in nodejs/undici

Package

npm undici (npm)

Affected versions

>= 6.0.0, < 6.24.0
>= 7.0.0, < 7.24.0

Patched versions

6.24.0
7.24.0

Description

Impact

A 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.

Workarounds

There are no workarounds.

References

@mcollina mcollina published to nodejs/undici Mar 12, 2026
Published by the National Vulnerability Database Mar 12, 2026
Published to the GitHub Advisory Database Mar 13, 2026
Reviewed Mar 13, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(20th percentile)

Weaknesses

Uncaught Exception

An exception is thrown from a function, but it is not caught. Learn more on MITRE.

Improper Validation of Specified Quantity in Input

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. Learn more on MITRE.

CVE ID

CVE-2026-1528

GHSA ID

GHSA-f269-vfmq-vjvj

Source code

Credits

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.