CVE-2026-120216
Description
A flaw was found in Fastify. An unauthenticated remote attacker can cause a Denial of Service (DoS) by sending a request to a streaming endpoint when a custom handler timeout is configured. If a streaming response remains open past the configured timeout after response headers have already been sent, the server attempts to issue an error on an active stream. This failure raises an unhandled exception that terminates the Node.js process and interrupts all in-flight requests.
Statement
This vulnerability is rated Moderate rather than Important because successful exploitation requires a non-default server configuration and is strictly limited to an availability impact. Under standard deployments, Fastify defaults to a handler timeout of 0, which leaves the application unaffected unless an administrator explicitly configures a non-zero timeout on streaming endpoints. Furthermore, exploitation results only in process termination without compromising confidentiality or allowing unauthorized data modification.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Read Application Data
An uncaught exception could cause the system to be placed in a state that could lead to a crash, exposure of sensitive information, or other unintended behaviors.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
